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OpenGL Need some pointers to my modification of Pauls Cel Shading program

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Hello, For the last couple of days I've been trying to modify Pauls (as in Cel Shading (the OpenGL version offcourse) example be able to handle multiple lights and colors (each light can have a diffrent color). So far I've managed to get the multiple lights working very good (just using the largest Dot product as the light to use), the shadows show very well and all. This is done the manual per Vertex lighting, not through ARB_vertex_program. Now, the colors are giving me a slight problem, mostly because I've never worked with Shaders before (not even this kind of shaders...). But the real problem is, they really are per vertex. And not smooth like the lighting. The most likly problem (or bottleneck) is that I'm assigning colors pretty much the same way as the vertexs. Namely through the use of a Color Array Pointer. Something else I would like to solve, is how to see if the vertex is occluded by something, so it doesn't get lit. And the last question is, how could I do something similar through a ARB_vertex_program shader (The one used under the button 2 of the program)? Thank you for your time, MLeoDaalder

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So what's not clear about my post?

Am I the only one having this problem and is it increadibly easy and is considerd that everyone knows how to do this?

How should I post questions anyway so that I might get a respond?
Just for future questions?

Thank you,


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Original post by zedzeek
i read your post a couple of times i still cant workout exactly what u want to do, perhaps a screenshot of what youve achieve sofar with a describtion of what u want to achieve

Now that's what I call constructive! Thanks!

Ok, here is what I have:
These show that I have successfully implented multiple lights.
And a very crude lighted colors...
Cel Shading 1
Cel Shading 2

My goal is to make the colors fluid as well.
And to check for occlusion.
As shown in this picture there isn't any.
Cel Shading 3
It's most noticable in the inner ring of the torus.

Thank you for your interrest!

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im a bad explained but anyways

>>My goal is to make the colors fluid as well.<<

u mean the blockiness (staircase effect) in red on the second picture?, i believe this is caused by u saturating the color for that vertice once the color value has gone above 1.0 its not going any higher

>>And to check for occlusion.<<

thus u only want the light to affect pieces of the mesh that actually would recieve that light ie theyre not being blocked by other parts of the mesh, if thats the case then u need to look into shadowing techniques. ie if a pixel is in shadow then dont let that light contribute to its shading

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Original post by zedzeek
im a bad explained but anyways

>>My goal is to make the colors fluid as well.<<

u mean the blockiness (staircase effect) in red on the second picture?, i believe this is caused by u saturating the color for that vertice once the color value has gone above 1.0 its not going any higher

In any of the colored parts.
The original color is r: 0.85, g: 0.75, b: 1.0
The upper left light has the color white.
The middle has the color: 1.0f, 0.0f, 0.5f
The upper right light has the color 1.0f, 1.0f, 0.0f

And this is my color/lighting part.

// Setting the initial color
for(int i=0;i<(torus.numVertices * 3);i+=3)
colorCoefficients[i ] = 0.95f;
colorCoefficients[i+1] = 0.75f;
colorCoefficients[i+2] = 1.0f;
//colorCoefficients[i] = float((double)i / (double)(torus.numVertices * 3.0));
//0.75f, 0.95f, 1.0f
int z=0;
for(i=0; i<torus.numVertices; i++)
lightCoefficients[i] = 0.0f;
for(int j=0; j<8; j++)
if(!(lightPositions[j].x == 0 && lightPositions[j].y == 0 && lightPositions[j].z == 0))
VECTOR3D lightDirection=(VECTOR3D(inverseModelMatrix*lightPositions[j])-torus.vertices[i].position).
if(torus.vertices[i].normal.DotProduct(lightDirection) > lightCoefficients[i])
lightCoefficients[i] = torus.vertices[i].normal.DotProduct(lightDirection);
if(!(lightColors[j].x == 0 && lightColors[j].y == 0 && lightColors[j].z == 0))
//colorCoefficients[z ] += (float(lightColors[j].x) * torus.vertices[i].normal.DotProduct(lightDirection));
//colorCoefficients[z+1] += (float(lightColors[j].y) * torus.vertices[i].normal.DotProduct(lightDirection));
//colorCoefficients[z+2] += (float(lightColors[j].z) * torus.vertices[i].normal.DotProduct(lightDirection));
colorCoefficients[z ] += float(lightColors[j].x);
colorCoefficients[z+1] += float(lightColors[j].y);
colorCoefficients[z+2] += float(lightColors[j].z);
colorCoefficients[z ] /= 2.0f;
colorCoefficients[z+1] /= 2.0f;
colorCoefficients[z+2] /= 2.0f;
z += 3;

I tried to use the vector class (the dynamic array one), but something is wrong with it, so any light at 0,0,0 or a black light is not shown.

I know this isn't the best way... It's my first program trying to make my own light...

>>And to check for occlusion.<<

thus u only want the light to affect pieces of the mesh that actually would recieve that light ie theyre not being blocked by other parts of the mesh, if thats the case then u need to look into shadowing techniques. ie if a pixel is in shadow then dont let that light contribute to its shading

Thanks for the pointer!

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Well, an update to the occlusion test...
I modified it from the Lensflare occlusion test (NeHe lesson 44).
And one thing I can say, it's killing my fps big time!
From about 85 to 20...
And it provides a completly occluded object...

But I also think this is a dual pass test.
Which means I will have to render the entire object for every light in the scene.

I suppose there isn't an better way?
Like a Vertex/Face Database?

After some more fidling I got the framerate down to 0.20...
And for some reason I find this funny.

And here is my occlusion test routine.
If I remove the glClear then I can see (sort of) what the light must see.

bool CheckShadow(TORUS* o, VECTOR3D* p, VECTOR3D* pos, VECTOR3D *dir)

//draw torus
glDrawElements(GL_TRIANGLES, o->numIndices, GL_UNSIGNED_INT, o->indices);

// Translate to the light position
glTranslated(pos->x, pos->y, pos->z);
// Rotate to the light direction
glRotated(1.0f, dir->x, dir->y, dir->z);

GLint viewport[4]; //space for viewport data
GLdouble mvmatrix[16], projmatrix[16]; //space for transform matricex
GLdouble winx, winy, winz; //space for returned projected coords
GLdouble flareZ; //here we will store the transformed flare Z
GLfloat bufferZ; //here we will store the read Z from the buffer

glGetIntegerv (GL_VIEWPORT, viewport); //get actual viewport
glGetDoublev (GL_MODELVIEW_MATRIX, mvmatrix); //get actual model view matrix
glGetDoublev (GL_PROJECTION_MATRIX, projmatrix); //get actual projiection matrix

gluProject(p->x, p->y, p->z, mvmatrix, projmatrix, viewport, &winx, &winy, &winz);
flareZ = winz;

// we read back one pixel from th depth buffer (exactly where our flare should be drawn)
glReadPixels(winx, winy,1,1,GL_DEPTH_COMPONENT, GL_FLOAT, &bufferZ);



if (bufferZ < flareZ)
return true;
return false;

And after some commenting stuff out I've found that glClear and glDrawElements are the things that slow it down.

[Edited by - mldaalder on November 27, 2004 9:38:01 AM]

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I've tried a couple of things for the shadow checking, but I haven't found it (yet)...
With it I mean a working method (not to speak of the FPS).

I also tried another implementation of the light colors.
I tried to use 3 1D textures. Representing Red, Green and Blue.
I thought of using multi texturing, but I figured out that they would cancel each other out because OpenGL fills in 0s for each missing component in glTexImage1D.

I've also tried 3D textures, but they didn't show up and (I calculated) to get a proper colors I'd have to use a texture with the size of:
256*256*256*3 = ~50MB.
Not a really good idea considering I have a 128MB Video card. :P

So any idea's for both of these 2 problems?
Or any basic ARB_fragment_program tutorials?

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