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AlphaDude

OpenGL Shadow Map CG - Help

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Hi! I am trying to implement a basic hardware shadow map using the example from the "Cg Tutorial" book... Here is the vertex shader:
 
struct VertexOut{
      float4 oPosition : POSITION;
      float4 texCoordProj : TEXCOORD0;
      float4 diffuseLighting : TEXCOORD1;
};

VertexOut ShadowMapVert(float4 position : POSITION,
                                     float3 normal : NORMAL,
                                     uniform float4x4 modelViewProj,
                                     uniform float3 lightPosition, 
                                     uniform float4x4 textureMatrix)
{

      VertexOut Oute;
      Oute.oPosition = mul(modelViewProj, position);
      float3 lightDirection = normalize(lightPosition - position.xyz);
      Oute.diffuseLighting = dot(lightDirection, normal);
      // Compute texture coordinates for 
      // querying the shadow map
      Oute.texCoordProj = mul(textureMatrix, position);
      return Oute;
}


..and the fragment counterpart:
 
struct FragmentOut
{
   float4 color : COLOR;
};

FragmentOut ShadowMapFrag(float4 col : COLOR IN, 
                                        float4 texCoordProj    : TEXCOORD0,
                                        float4 diffuseLighting : TEXCOORD1,          
                                        uniform sampler2D ShadowMap)
{
      FragmentOut Out;
      // Fetch color from the projective texture
      float4 projColor = tex2Dproj(ShadowMap, texCoordProj);

      Out.color = projColor * diffuseLighting;

      return Out;
}


The OpenGL texture setup:
 
      glEnable(GL_TEXTURE_2D);
      glGenTextures(1, &shadowMapTexture);
      glBindTexture(GL_TEXTURE_2D, shadowMapTexture);
      glTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT16_ARB, shadowMapSize, shadowMapSize, 0,
      GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, NULL );

      glTexParameteri(GL_TEXTURE_2D,GL_DEPTH_TEXTURE_MODE,GL_INTENSITY);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);


and finally the render from light:
 
...
RenderWorld(update);

glBindTexture(GL_TEXTURE_2D, shadowMapTexture);

glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, shadowMapSize, shadowMapSize); 
...


The problem I am having is that no depth comparison takes place on the fragment shader, I'm lead to believe that I have not set the opengl texture parameters correctly or something... can someone explain to me what I have done wrong or missed out ? P.S: I am a total nooooob Thank you [Edited by - AlphaDude on April 18, 2006 1:31:51 PM]

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A screenshot of what is happening versus what you want could help us.

So I have not read through the code but what you want to do is use a texture for shadow mapping using the technique described in the book.

Is it the technique where the shadow map is projects from the light's view point?

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as far as I remember the depth comparison has changed between DX8 and DX9 ... I am not quite sure if that also influenced the OGL implementation. I would just revert the comparison to try this out ....
Just a shot in the dark ...

- Wolf

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Quote:
Original post by wolf
as far as I remember the depth comparison has changed between DX8 and DX9 ... I am not quite sure if that also influenced the OGL implementation. I would just revert the comparison to try this out ....
Just a shot in the dark ...

- Wolf


Hi Wolf, thanks for replying..

This is what I get:

http://img417.imageshack.us/my.php?image=shad9bd.png

I would like some shadowing to take place! ... lol

The problem im having, is that after projecting the depth texture onto the scene, the depth comparison appears to have no effect and nothing is in shadow. It appears as if the depth texture is only 1's, or nothing has been written into it.

After spending a long time searching the net for any idea of what might be wrong, I found someone else had a similar problem to mine and he added these lines of code to get it working:

glActiveTextureARB(GL_TEXTURE4_ARB);
glEnable(GL_TEXTURE_2D);
glTexEnvi(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_COMPARE_MODE_ARB,GL_COMPARE_R_TO_TEXTURE);

But when I do the same, it makes no difference.. I am pretty sure it is something to do with the setting up from Opengl side of things...


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What texture matrix are you using to send in the shadow matrix as? It looks like you are using


glActiveTextureARB(GL_TEXTURE4_ARB);
glEnable(GL_TEXTURE_2D);
glTexEnvi(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_COMPARE_MODE_ARB,GL_COMPARE_R_TO_TEXTURE);



I don't have access to the rest of your code so which unit are you doing your matrix manipulation under? And which one are you sending to the Cg shader?

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Hi Mars,

I have included some more code to make it easier:

Set up the cg parameters:

 
// bind parameters - vertex:
cgModelViewProj = cgGetNamedParameter(cgVertexShader, "modelViewProj");
cgLightPosition = cgGetNamedParameter(cgVertexShader, "lightPosition");
cgTextureMatrix = cgGetNamedParameter(cgVertexShader, "textureMatrix");

// bind parameters - fragment
cgShadowMap = cgGetNamedParameter(cgFragmentShader, "ShadowMap");

static MATRIX4X4 biasMatrix(0.5f, 0.0f, 0.0f, 0.0f,
0.0f, 0.5f, 0.0f, 0.0f,
0.0f, 0.0f, 0.5f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f);

//bias from [-1, 1] to [0, 1]
MATRIX4X4 textureMatrix = biasMatrix*lightProjectionMatrix*lightViewMatrix;

//Calculate texture matrix for projection
cgGLSetParameter4fv(cgTextureMatrix,textureMatrix);
cgGLSetParameter4fv(cgLightPosition, lightPos);






// Main rendering:

void ShadowMap::drawMap(){	

cgGLEnableProfile(cgVertexProfile);
cgGLBindProgram(cgVertexShader);

cgGLEnableProfile(cgFragmentProfile);
cgGLBindProgram(cgFragmentShader);

// First pass - from light's point of view

renderShadowMap();

// Second pass - from camera's point of view

renderFromCamera();
angle +=1.0;

cgGLDisableTextureParameter(cgShadowMap);
cgGLDisableProfile(cgVertexProfile);
cgGLDisableProfile(cgFragmentProfile);
}

void renderShadowMap(){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDepthFunc(GL_LEQUAL);

glMatrixMode(GL_PROJECTION);
glLoadMatrixf(lightProjectionMatrix);
glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(lightViewMatrix);

glViewport(0, 0, shadowMapSize, shadowMapSize);

glCullFace(GL_FRONT);
glShadeModel(GL_FLAT);
glColorMask(0, 0, 0, 0);

//glFrontFace(GL_CW);
glEnable(GL_CULL_FACE);

RenderWorld(update);
glBindTexture(GL_TEXTURE_2D, shadowMapTexture);
glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, shadowMapSize, shadowMapSize);

//restore states
glCullFace(GL_BACK);
glShadeModel(GL_SMOOTH);
glColorMask(1, 1, 1, 1);

glClear(GL_DEPTH_BUFFER_BIT);
glDisable(GL_TEXTURE_2D);
}

void renderFromCamera(){

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_PROJECTION);
glLoadMatrixf(cameraProjectionMatrix);
glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(cameraViewMatrix);

glViewport(0, 0, 640, 480);

RenderWorld(update2);
}

void update(){
cgGLSetStateMatrixParameter(cgModelViewProj, CG_GL_MODELVIEW_PROJECTION_MATRIX, CG_GL_MATRIX_IDENTITY);
}

void update2(){
cgGLSetStateMatrixParameter(cgModelViewProj, CG_GL_MODELVIEW_PROJECTION_MATRIX, CG_GL_MATRIX_IDENTITY);
cgGLSetTextureParameter(cgShadowMap,shadowMapTexture);
cgGLEnableTextureParameter(cgShadowMap);
}




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Well I am confused, it looks like you are using texture unit 4 in the one example to do your comparisons, and then you are sending the texture matrix in as a matrix4x4 to Cg... I wonder if you don't have your matrix setup right... I don't see your camera inverse matrix either?

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Hi,

I did this awhile ago and had many of the same problems. My first recommendation would be to try project just a normal texture, not a depth map. This way you can find out if your matrices are correct. Also shouldn't you have your shaders turned off when you render your depth map? Try useing gdebugger to look at your depth map when your program is running.

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Hi RocketTree, Thanks for replying to my thread...

http://www.gamedev.net/community/forums/topic.asp?topic_id=388043

I have changed my code:

OpenGL depth map initiation:

	glGenTextures(1, &shadowMapTexture);
glBindTexture(GL_TEXTURE_2D, shadowMapTexture);
glTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT16_ARB, shadowMapSize, shadowMapSize, 0,
GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, NULL );
glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE_ARB,GL_INTENSITY);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

glActiveTextureARB(GL_TEXTURE4_ARB);
glTexEnvi(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE);
glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE_ARB, GL_INTENSITY);


Main rendering:


void ShadowMap::drawMap(){

glEnable(GL_TEXTURE_2D);

// First pass - from light's point of view
renderShadowMap();

cgGLEnableProfile(cgVertexProfile);
cgGLBindProgram(cgVertexShader);

cgGLEnableProfile(cgFragmentProfile);
cgGLBindProgram(cgFragmentShader);

// Second pass - from camera's point of view

renderFromCamera();

glDisable(GL_TEXTURE_2D);

angle +=1.0;
cgGLDisableTextureParameter(cgShadowMap);
cgGLDisableProfile(cgVertexProfile);
cgGLDisableProfile(cgFragmentProfile);
}

void renderShadowMap(){

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDepthFunc(GL_LEQUAL);

glMatrixMode(GL_PROJECTION);
glLoadMatrixf(lightProjectionMatrix);

glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(lightViewMatrix);

glViewport(0, 0, shadowMapSize, shadowMapSize);

glCullFace(GL_FRONT);
glShadeModel(GL_FLAT);
glColorMask(0, 0, 0, 0);

//glFrontFace(GL_CW);
glEnable(GL_CULL_FACE);

RenderWorld(update);
glBindTexture(GL_TEXTURE_2D, shadowMapTexture);
glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, shadowMapSize, shadowMapSize);

//restore states
glCullFace(GL_BACK);
glShadeModel(GL_SMOOTH);
glColorMask(1, 1, 1, 1);
}

void renderFromCamera(){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_PROJECTION);
glLoadMatrixf(cameraProjectionMatrix);

glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(cameraViewMatrix);

glViewport(0, 0, 640, 480);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE_ARB, GL_COMPARE_R_TO_TEXTURE_ARB);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC_ARB, GL_LEQUAL);

static MATRIX4X4 biasMatrix(0.5f, 0.0f, 0.0f, 0.0f,
0.0f, 0.5f, 0.0f, 0.0f,
0.0f, 0.0f, 0.5f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f);

textureMatrix = biasMatrix*lightProjectionMatrix*lightViewMatrix ;

glMatrixMode(GL_TEXTURE);
glLoadMatrixf(textureMatrix);

RenderWorld(update2);

void update(){
}

void update2(){
cgGLSetStateMatrixParameter(cgTextureMatrix, CG_GL_TEXTURE_MATRIX, CG_GL_MATRIX_IDENTITY);
cgGLSetStateMatrixParameter(cgModelViewProj, CG_GL_MODELVIEW_PROJECTION_MATRIX, CG_GL_MATRIX_IDENTITY);

cgGLSetTextureParameter(cgShadowMap,shadowMapTexture);
cgGLEnableTextureParameter(cgShadowMap);
}





The current results:

The scene as it should look like without shadows:

The scene as it should look like without shadows

But this is what I get with shadows turned on:
This is what I get with shadows turned on


Looks to me like the shadow is being projected but the actual scene is not there and being projected correctly and I can't for the life of me figure out what I have done wrong in the setting up of texture matrix... so is it possible for you to check where I have gone wrong?...I mean if it is not too much trouble...or show me your implementation of the shadow map... just the relevant bits? I would'nt normally ask this kind of thing but it is just driving me nuts and I have spent about 4 days on this with no improvement... I would really appreciate any help you can give.

Thank you

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