KR20030014516A - apparatus and method for processing bump mapping - Google Patents

Abstract

PURPOSE: A system and a method for processing bump mapping are provided to reduce the amount of computation with respect to bump mapping using polar coordinate system. CONSTITUTION: A system for processing bump mapping includes the first and second computation units and a memory. The first computation unit receives a direction vector value of an incident light with respect to a polygon to be mapped, an intermediate vector value of the direction vector value and a point vector value, and a vertical vector value, and converts the direction vector value and intermediate vector value from a three-dimensional object space into a three-dimensional bump space. The memory stores a bump vector map having a perturbed normal vector value of pixels for the polygon and a look-up table having parameters. The second computation unit receives the converted direction vector value and intermediate vector value from the first computation unit and reads the perturbed normal vector value and required parameters from the bump vector map and memory, to compute a color value of each pixel of the polygon.

Description

Apparatus and method for processing bump mapping}

The present invention relates to a three-dimensional graphics accelerator system, and more particularly to a bump mapping apparatus and method for realistic image processing.

Currently, texture mapping, bump mapping, environment mapping, displacement mapping, etc. are used for realistic image processing in most 3D graphics accelerator systems.

Among them, texture mapping is the most commonly used method. By giving a pattern to the surface of an object, it gives a certain degree of realism to the object.

Adding a bend or reflection effect to these textures creates a much more realistic image.

Bump mapping is a technique that adds bumpy curvature to the surface of a flat object for such realistic images.

This is useful for expressing complex objects through simple geometry mapping without modeling complex objects.

1 is a diagram illustrating a general bump mapping method.

The prior art is basically performed through two processes as shown in FIG.

The first process is to transform a normal vector from local space information, and the second process is to calculate a pixel color value that is an illumination value from the modified normal vector and illumination parameters.

Finally, bump mapping is performed according to pixel color values.

In more detail, the first process is a process of perturbing a normal vector N perpendicular to a tangent plane at an point on an object in a direction perpendicular to a curved surface. Calculate N '.

N '= N + B _u (N × P _v )-B _v (N × P _u )

In order to perform the process parameters at a point P above the object variables u, v a tangent plane (tangent plane) vector P _u, P _v and direction parameters in the above to be a bump map mapped to a point on the partial derivatives of variables u We need the slopes B _u , B _v for, _v .

This process requires considerable computational logic and computational amount in the bump mapping process.

The second process is to calculate a new light for the modified normal vector N 'as described above, and is calculated based on the Phong Illumination Model.

The Phong lighting model is designed to reflect ambient light incident from the environment, diffuse light from the interaction of the incident light with the molecules that make up the object surface, and the specular surface reflected from the shiny, shiny object's surface. It consists of specular light.

Therefore, as shown in Equations 2, 3, and 4, the ambient light I _g , the diffused light I _d , and the specular light I _s are calculated.

Ambient light I _g = I _a k _a

Where I _a is the intensity of ambient light and k _a is the ambient coefficient.

Diffused light I _d = I _i k _d cosθ 0≤θ≤2π

= I _i k _d (LN)

Where I _i is the light intensity of the light source, k _d is the diffusion coefficient, L is the direction vector of the incident light, and N is the surface normal vector.

Mirror light I _s = I _i k _s cos ⁿ Ω

= I _i k _s (RV) ⁿ

Where k _s is the mirror coefficient, n is the reflectance, R is the direction vector of the reflected light, and V is the direction vector of the viewpoint.

As such, the illumination value I is determined using the calculated value as shown in Equation 5 below.

I = I _g + I _d + I _s

= I _a k _a + I _i (k _d (L · N) + k _s (R · V) ⁿ )

Bump mapping is completed by performing color processing on each pixel using the determined illumination value.

However, this method has a complicated calculation and a large amount of calculation, which increases the cost of bump mapping.

Therefore, a method of using a low computation vector H instead of a high computation vector R has been proposed to reduce the cost for bump mapping.

The vector H is a unit normal vector of a virtual surface directed in the middle direction between the light direction vector L and the viewpoint vector V as shown in Equation 6 below.

H = (L + V) / 2

Using the vector H, the lighting value I is calculated as shown in Equation 7 below.

I = I _g + I _d + I _s

= I _a k _a + I _i (k _d (LN) + k _s (RH) ⁿ )

However, such a bump mapping method also requires a considerable amount of computation, and thus the structure of the bump mapping algorithm and hardware is complicated, and the mapping process cost is also increased.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and an object thereof is to provide a bump mapping processing apparatus and method having a simple bump mapping processing algorithm and a hardware structure.

1 is a view illustrating a general bump mapping process

2 is an illustration of bump mapping according to the present invention;

3 is a flow chart for processing bump mapping in accordance with the present invention.

4 is a block diagram for processing bump mapping according to the present invention.

5 is a block diagram illustrating a bump mapping apparatus according to the present invention;

6 is a flow chart showing a rendering process performed with bump mapping according to the present invention.

The bump mapping method according to the present invention receives a direction vector value L, an intermediate vector value H of the direction vector value L, a viewpoint vector value V, and a vertical vector value N of the incident light with respect to a polygon to be externally mapped. Calculating the value L 'and the intermediate vector value H' to be converted from the 3D object space to the 3D bump space, and receiving the converted direction vector value L 'and the intermediate vector value H' and storing the bump vector map in memory. And calculating each pixel color value of the polygon to be mapped by reading the modified normal vector value N 'of the pixel for the polygon from the required parameters from the look-up table stored in memory.

In the step of calculating the direction vector value L and the intermediate vector value H to be converted from three-dimensional object space to three-dimensional bump space, the vertical vector value N is In other words, the converted direction vector value L ' And the transformed intermediate vector value H ' to be.

In addition, the step of calculating each pixel color value of the polygon to be mapped includes the transformed normal vector value N of the pixel for the polygon from the bump vector map stored in memory after receiving the converted direction vector value L 'and the intermediate vector value H'. ', And calculate these to obtain the diffused light direction vector D and the specular light direction S of the corresponding pixel, and read the required parameters from the cosine table and the power table of the look-up table stored in the memory and compute these to diffuse Calculating the intensity of the light and the specular light, receiving the parameters of the light applied from the outside, and multiplying them by the calculated diffuse and specular light, respectively, and then adding the intensity of the multiplied diffused light and the specular light to add the color of the corresponding pixel. The process consists of finding the value.

Here, the direction vector D of the diffused light subtracts the modified normal vector value N 'to the converted direction vector value L', and the direction vector S of the specular light subtracts the converted intermediate vector value H 'to the modified normal vector value N'. do.

The bump mapping apparatus according to the present invention receives the direction vector value L, the direction vector value L, the intermediate vector value H of the direction vector value L and the viewpoint vector value V, and the vertical vector value N of the incident light with respect to the polygon to be externally mapped. A first computing unit for converting the value L 'and the intermediate vector value H' from 3D object space to 3D bump space, and a bump vector map and parameters having the modified normal vector values N 'of the pixel for the polygon. A modified normal vector value N of pixels for a polygon from a memory unit having a look-up table having a look-up table and a direction vector value L 'and an intermediate vector value H' converted from a first calculator and a bump vector map stored in the memory unit And a second operation unit for reading the required parameters from the look-up table stored in the memory and calculating each pixel color value of the polygon to be mapped.

Here, the first calculator receives the direction vector value L of the incident light with respect to the polygon to be mapped from the outside, the intermediate vector value H of the direction vector value L, the viewpoint vector value V, and the vertical vector value N, and receives the direction vector value L '. And four subtractors for subtracting the intermediate vector value H 'from three-dimensional object space to three-dimensional bump space. The second operation unit receives the converted direction vector value L' and the intermediate vector value H ', and stores the memory. An adder / subtracter that reads the modified normal vector values N 'of the pixels for the polygons from the bump vector map stored in the part and the required parameters from the look-up table stored in the memory part, subtracts and adds them, and is applied from the outside. And first and second multipliers that multiply the parameters of the light and the result value calculated from the adder / subtracter, and an adder that adds the result values calculated from the first and second multipliers.

Also, the second operation unit receives a look-up table having first and second cosine tables and a power table, and converts a direction vector value L 'and an intermediate vector value H' into a polygon from a bump vector map stored in a memory unit. Read the modified normal vector value N 'of the pixel and the necessary parameters from the look-up table, and add / subtract them to subtract them, and calculate the result values from the externally applied parameters and adders / subtracters. The multiplier may include a first multiplier and a multiplier and an adder for adding the result values calculated from the first multiplier and the second multiplier.

As described above, the present invention has the advantage of significantly reducing the hardware required to determine the color of the object and the transformation of the vector into the tangent plane space required for bump mapping compared to the conventional Cartesian coordinate system.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Referring to the accompanying drawings, preferred embodiments of the present invention having the features as described above are as follows.

First of all, the concept of the present invention can implement a bump mapping processing apparatus having an excellent price-to-performance ratio by reducing the amount of computation for bump mapping and reducing hardware according to the polar coordinate system instead of the conventional Cartesian coordinate system.

The algorithm for performing bump mapping according to the present invention is largely divided into two parts as shown in FIG. 2.

First, in preparation for performing bump mapping, a process of converting a light vector L and an intermediate vector H into a bump vector space is performed.

This only needs to be done once when the polygon, which is the processing unit of the scan conversion, is entered.

In this process, the position P is moved to the bump vector space, which is the unit space of the polygon, at a geometric position, thereby ensuring position-independent performance.

In particular, this process can be performed in overlap with the scan conversion process.

That is, it means that the overhead due to the addition of bump mapping can be reduced.

The following process is a routine for processing each pixel for the polygon to be mapped. The modified normal vector N 'of the pixel is obtained from the bump vector map using the bump map address calculated in the scan conversion process. The color value of the pixel (light intensity) is calculated by combining the direction vector L 'and the intermediate vector H' of the converted light through the polygon process.

In this process, the Phong lighting model is applied to calculate the light intensity.

That is, the second process is repeated to obtain the color value of the entire pixel of the polygon using two constant vectors L 'and H' of the polygon and a normal vector N 'which continuously changes along the polygon.

3 is a flowchart for processing bump mapping according to the present invention, and FIG. 4 is a block diagram for processing bump mapping according to the present invention.

As shown in Figures 3 and 4, the first step is a vector rotation unit, which is responsible for converting the geometry on the object space into bump vector space.

The next step is to obtain the modified normal vector of the corresponding pixel from the bump vector map using the bump map address obtained through the scan conversion process.

The final step is to calculate the bump-mapped color value of the pixel by receiving the vectors from the first and second steps based on the Phong illumination model and the table method as the illumination unit.

A more detailed description is as follows.

The vector rotation step performs a transformation from a 3D object space to a 3D bump space.

Input rotational value N of direction vector L and intermediate vector H of light in object space Rotate simply to convert to L 'and H' in bump space.

Here, the normal vector of the polygon is N: Say,

L:

H:

to be.

Next, a bump vector loading step is performed to bring the inclined normal vector from the bump map with the bump vector map address of each pixel generated through the scan conversion process.

As described above, the bump vector map may be configured on the tangent plane of the object.

This means that the bump map can be constructed regardless of the position of the object.

The composition of this map is calculated offline using the usual method.

The array format of each vector is the same as the existing texture map, but the size of each cell is composed of 32 bits to store a normal vector value.

Lastly, the illumination computation step is to obtain pixel color values of polygons to be actually mapped using the vectors L ', H', and N 'obtained through the above two steps.

In this step, the intensity calculation of diffused and specular light is used to calculate pixel color values to be bump mapped.

The intensity of the diffused light from the input of the rotated (transformed) direction vector L ', the intermediate vector H' calculated from the vector rotation unit, the perturbed normal vector from the bump map, and several parameters of the Phong illumination model. And the intensity of the specular light.

The intensity of diffused light and the intensity of specular light are based on the Phong lighting model and are largely divided into inner product operation and power operation.

These two operations basically handle the operation simply through a look-up table (LUT) reference.

The processing of the dot product is handled by subtracting the vector and referencing the cosine table.

Subtraction of the vector is calculated as follows.

Diffuse Light Vector D = L '-N', Specular Light Vector S = N '-H'

The angles of the diffused light and the specular light through the cosine table reference are as follows.

The power operation is processed through a reference to a simple cosine power table.

This is to reduce the delay and the increase of the calculation amount due to the power calculation calculation.

That is, the steps of calculating each pixel color value of the polygon to be mapped in detail are as follows.

The transformed direction vector value L 'and the intermediate vector value H' are inputted, and the modified normal vector value N 'of the pixel for the polygon is read from the bump vector map stored in the memory, and these are calculated to calculate the diffuse light direction vector of the pixel. After obtaining the direction vector S of D and the specular light, the necessary parameters are read from the cosine table and the power table of the look-up table stored in the memory, and these are calculated to obtain the intensity of diffused and specular light.

Then, the parameters of the light applied from the outside are input, and these are multiplied by the calculated intensity of diffused light and specular light, respectively, and the intensity of the multiplied diffused light and the intensity of specular light are added to obtain a color value of the corresponding pixel.

5 is a block diagram illustrating a bump mapping apparatus according to the present invention.

As shown in FIG. 5, a first operation unit, a second operation unit, and a memory unit are largely configured.

Here, the first calculator receives the direction vector value L of the incident light with respect to the polygon to be mapped from the outside, the intermediate vector value H of the direction vector value L, the viewpoint vector value V, and the vertical vector value N, and receives the direction vector value L '. And four subtractors for subtracting the intermediate vector value H 'from three-dimensional object space to three-dimensional bump space.

The second operation unit receives the transformed direction vector value L 'and the intermediate vector value H', and the modified normal vector value N 'of the pixel for the polygon from the bump vector map stored in the memory unit and the look stored in the memory unit- First and second multipliers for reading the necessary parameters from the up table, subtracting and adding them, multiplying the parameters of light applied from the outside with the result calculated from the adder / subtracter, and And an adder for adding the result values calculated from the second multiplier.

The memory section also stores a bump vector map with modified normal vector values N 'of pixels for the polygon, and a look-up table with parameters.

Here, the look-up table is composed of a first, a second cosine table, and a power table. The look-up table may not be configured in the memory unit but may be arranged separately in the second calculator.

In addition, the present invention can be carried out in combination with the overall rendering process.

6 is a flowchart illustrating a rendering process performed with bump mapping according to the present invention.

As shown in FIG. 6, local space information is a value input during a geometric processing process for processing in a bump vector space and used for rotation of a vector.

In the present invention, the vector rotation process is performed in overlap with the scan conversion process.

Also, in the mapping process, texture mapping and bump mapping are performed at the same time.

As described above, the bump mapping processing apparatus and method according to the present invention have the following effects.

First, in order to take advantage of the ease of geometry processing (transformation and light intensity calculation) and small amount of data movement for vectors requiring only directions, such as the direction vector L of light, the middle vector H, and the vertical vector N of polygons. Expressed in polar coordinates.

This makes it possible to calculate the vector matrix multiplication process and the light intensity process through the angles of two vectors required for the processing of transformation and lighting in the conventional Cartesian coordinate system by simple arithmetic operation. The vectorization process was removed.

In addition, by representing the vector by two coordinates, the amount of movement of the actual data can be reduced.

And, the use thereof can reduce the complexity of hardware.

Second, an effective rendering structure incorporating the bump mapping hardware of the present invention can be cited.

By performing the bump mapping process and the scan conversion process in parallel, it is possible to reduce the execution time delay due to the bump mapping support as compared to the conventional sequential processing method.

In the case of the sequential processing method, it is necessary to keep unnecessary data in the fragment queue for a long time to process the pixel data at execution time.

However, by performing parallel processing as in this structure, it is possible to maintain and distribute useful data in the fragment queue.

As such, by reducing the processing time, it is possible to effectively process the rendering process and the mapping process.

In addition, the bump vector map generated offline and the present structure may make the bump mapping execution time almost equal to the texture mapping execution time.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (8)

In the bump mapping processing method of the bump mapping processing apparatus which has a memory part and an operation part, The direction vector value L of the incident light with respect to the polygon to be mapped from the outside, the intermediate vector value H of the direction vector value L, the viewpoint vector value V, and the vertical vector value N are received, and the direction vector value L 'and the intermediate vector value are received. Calculating H 'to be converted from three-dimensional object space to three-dimensional bump space; As a result of the operation, the transformed direction vector value L 'and the intermediate vector value H' are input, and the modified normal vector value N 'of the pixel for the polygon from the bump vector map stored in the memory and the look-up stored in the memory And calculating a pixel color value of the polygon to be mapped by reading necessary parameters from a table. The method of claim 1, wherein in the step of calculating the direction vector value L and the intermediate vector value H to be converted from three-dimensional object space to three-dimensional bump space, The vertical vector value N is In other words, the converted direction vector value L ' And the transformed intermediate vector value H ' Bump mapping processing method characterized in that. The method of claim 1, wherein calculating each pixel color value of the polygon to be mapped is performed. The transformed direction vector value L 'and the intermediate vector value H' are inputted, and the modified normal vector values N 'of pixels for the polygon are read from the bump vector map stored in the memory, and these are calculated to calculate the values of the corresponding pixel. Obtaining the diffused light direction vector D and the direction vector S of the specular light; Reading required parameters from a cosine table and a power table of the look-up table stored in the memory, and calculating them to obtain the intensity of the diffused and specular light; Receiving parameters of light applied from the outside, multiplying them by the calculated intensity of diffused light and specular light, and then calculating the color value of the corresponding pixel by adding the intensity of the multiplied diffused light and the intensity of specular light; Bump mapping processing method, characterized in that. 4. The method of claim 3, wherein the direction vector D of the diffused light is subtracted from the modified normal vector value N 'to the transformed direction vector value L', and the direction vector S of the specular light is reduced to the modified normal vector value N '. Bump mapping processing method characterized in that the subtraction of the transformed intermediate vector value H '. The direction vector value L of the incident light with respect to the polygon to be mapped from the outside, the intermediate vector value H of the direction vector value L, the viewpoint vector value V, and the vertical vector value N are received, and the direction vector value L 'and the intermediate vector value are received. A first calculating unit which calculates H 'to be converted from a 3D object space into a 3D bump space; A memory portion storing a bump vector map having modified normal vector values N 'of pixels for the polygon and a look-up table having parameters; The transformed normal vector value N 'of the pixel for the polygon and the look stored in the memory are received from the first vector operation unit, the transformed direction vector value L' and the intermediate vector value H 'are received from the bump vector map stored in the memory unit. And a second calculating part which reads out necessary parameters from the up table and calculates each pixel color value of the polygon to be mapped. The method of claim 5, wherein the first operation unit receives a direction vector value L of the incident light with respect to the polygon to be mapped from the outside, an intermediate vector value H of the direction vector value L and the viewpoint vector value V, and a vertical vector value N. And four subtractors configured to subtract the direction vector value L 'and the intermediate vector value H' from 3D object space to 3D bump space. The method of claim 5, wherein the second operation unit The transformed normal vector value N 'of the pixel for the polygon is received from the bump vector map stored in the memory unit and the look-up table stored in the memory unit. An adder / subtractor that reads the necessary parameters from the subtracter and subtracts them; First and second multipliers for multiplying parameters of light applied from the outside by a result value calculated from the adder / subtracter; And a adder configured to add result values calculated from the first and second multipliers. The method of claim 5, wherein the second operation unit A look-up table having a first and a second cosine table, a power table; The transformed direction vector value L 'and the intermediate vector value H' are input, and the necessary parameter is obtained from the modified normal vector value N 'of the pixel for the polygon and the look-up table from the bump vector map stored in the memory unit. Adder / subtracter to read them and subtract and add them; First and second multipliers for multiplying parameters of light applied from the outside by a result value calculated from the adder / subtracter; And a adder configured to add result values calculated from the first and second multipliers.