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OpenGL Fixed Pipeline and Shadow Mapping

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Hi,

i am working on a OpenGL project and have problems with my shadows. They are not displayed and i dont know why. The code, which i use, is from http://www.paulsproj...ls/smt/smt.html .
The idea is:
I draw the scene three times. In the first draw, i write the depth values in a FBO from the lightview direction.
In the second draw, i draw the scene normal with (0.2, 0.2, 0.2, 1) light intensity.
In the third step i draw the scene with bright light and make a comparison with the depth values. Here is the code: The first part is my shadow class and the second part my viewer class. In the viewer class all draws etc. are handled.


void Shadows::generateShadowBuffer()
{
shadowMapSize = 512;

// Init texture
glGenTextures(1, &_depthTextureId);
glBindTexture(GL_TEXTURE_2D, _depthTextureId);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT24, shadowMapSize, shadowMapSize,
0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
glBindTexture(GL_TEXTURE_2D, 0);

// Init buffer
glGenFramebuffersEXT(1, &_fboId);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, _fboId);

// attach the texture to FBO color attachment point
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
GL_TEXTURE_2D, _depthTextureId, 0);

// Instruct openGL that we won't bind a color texture with the currently binded FBO
glDrawBuffer(GL_NONE);
glReadBuffer(GL_NONE);

// check FBO status
GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
if(status != GL_FRAMEBUFFER_COMPLETE_EXT)
printf("Buffer init wasnt correct.\n");

glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

// Check for Error
GLenum error = glGetError();
if(error != 0)
{
printf("Error occured in Shadows::generateShadowBuffer: %d\n", error);
if(GL_STACK_OVERFLOW == error)
printf("GL_STACK_OVERFLOW\n");
if(GL_STACK_UNDERFLOW == error)
printf("GL_STACK_UNDERFLOW\n");
}
}

// ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
void Shadows::drawFromLight(Vector lightPosition)
{
// Activate Buffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, _fboId);

// clear buffers
glClear(GL_DEPTH_BUFFER_BIT);
glColorMask(0, 0, 0, 0);

// Init matrices
glPushMatrix();
glLoadIdentity();
gluPerspective(60.0f, 1.0f, 0.1f, lightPosition.y + 10);
glGetFloatv(GL_MODELVIEW_MATRIX, _projectionMatrix);
glPopMatrix();

glPushMatrix();
glLoadIdentity();
gluLookAt(lightPosition.x, lightPosition.y, lightPosition.z,
lightPosition.x, 0, lightPosition.z,
0, 0, 1.0f);
glGetFloatv(GL_MODELVIEW_MATRIX, _lightviewMatrix);
glPopMatrix();

//Draw from the light's point of view
glViewport(0, 0, shadowMapSize, shadowMapSize);

glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadMatrixf(_projectionMatrix);

glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(_lightviewMatrix);

glPolygonOffset(8.0f, 1.1f);
glEnable(GL_POLYGON_OFFSET_FILL);

// Check for Error
GLenum error = glGetError();
if(error != 0)
{
printf("Error occured in Shadows::drawFromLight: %d\n", error);
if(GL_STACK_OVERFLOW == error)
printf("GL_STACK_OVERFLOW\n");
if(GL_STACK_UNDERFLOW == error)
printf("GL_STACK_UNDERFLOW\n");
}
}

// ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
void Shadows::drawWithShadows(int width, int height, Vector position, Vector direction, Vector up, float yPos)
{
// Deactivate buffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
/*glPopAttrib();
glBindTexture(GL_TEXTURE_2D, _depthTextureId);
GLfloat* buffer = new GLfloat[shadowMapSize * shadowMapSize];
glReadPixels(0, 0, shadowMapSize, shadowMapSize, GL_DEPTH_COMPONENT, GL_FLOAT, buffer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT24, shadowMapSize, shadowMapSize, 0, GL_DEPTH_COMPONENT, GL_FLOAT, buffer);

std::vector<float> pixbuf;
for(int i = 0; i < shadowMapSize*shadowMapSize; i++)
pixbuf.push_back(buffer);
for(int i = 0; i < pixbuf.size(); i++)
if(pixbuf != 1)
{
std::cout << pixbuf << std::endl;
}
delete[] buffer;*/

//Clear depth buffer

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Enable colorwriting
glColorMask(1, 1, 1, 1);

//reset viewport
glViewport(0, 0, width, height);

//Reset projection matrix
glMatrixMode(GL_PROJECTION);
glPopMatrix();

//Draw from camera's point of view
glMatrixMode(GL_MODELVIEW);
//glLoadMatrixf(viewMatrix);
glLoadIdentity();
gluLookAt(position.x, position.y, position.z,
direction.x, -direction.y, direction.z,
up.x, up.y, up.z);
glTranslatef(0, yPos, 0);

// Check for Error
GLenum error = glGetError();
if(error != 0)
{
printf("Error occured in Shadows::drawWithShadows: %d\n", error);
if(GL_STACK_OVERFLOW == error)
printf("GL_STACK_OVERFLOW\n");
if(GL_STACK_UNDERFLOW == error)
printf("GL_STACK_UNDERFLOW\n");
if(GL_INVALID_OPERATION == error)
printf("GL_INVALID_OPERATION\n");
if(GL_INVALID_VALUE == error)
printf("GL_INVALID_VALUE\n");
}
}

// ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
void Shadows::drawWithoutShadows()
{
//glActiveTexture(GL_TEXTURE7);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, _depthTextureId);

// Get matrix


GLfloat bias[16] = {
0.5, 0.0, 0.0, 0.0,
0.0, 0.5, 0.0, 0.0,
0.0, 0.0, 0.5, 0.0,
0.5, 0.5, 0.5, 1.0};

// concatinating all matrice into one.
MyMatrix dummy;
dummy = MyMatrix(bias) * MyMatrix(_projectionMatrix) * MyMatrix(_lightviewMatrix);

const GLfloat first[4] = {dummy[0], dummy[4], dummy[8], dummy[12]};
const GLfloat second[4] = {dummy[1], dummy[5], dummy[9], dummy[13]};
const GLfloat third[4] = {dummy[2], dummy[6], dummy[10], dummy[14]};
const GLfloat fourth[4] = {dummy[3], dummy[7], dummy[11], dummy[15]};

//Set up tex coord generation - all 4 coordinates required
glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_S, GL_EYE_PLANE, first);
glEnable(GL_TEXTURE_GEN_S);
glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_T, GL_EYE_PLANE, second);
glEnable(GL_TEXTURE_GEN_T);
glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_R, GL_EYE_PLANE, third);
glEnable(GL_TEXTURE_GEN_R);
glTexGeni(GL_Q, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_Q, GL_EYE_PLANE, fourth);
glEnable(GL_TEXTURE_GEN_Q);

//Use SGIX_shadow comparison
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_SGIX, true);

glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE_ARB, GL_INTENSITY);

//glBlendEquationEXT(GL_MAX_EXT);
//glEnable(GL_BLEND);
//Set alpha test to discard false comparisons
glAlphaFunc(GL_GEQUAL, 0.99f);
glEnable(GL_ALPHA_TEST);

// Check for Error
GLenum error = glGetError();
if(error != 0)
{
printf("Error occured in Shadows::drawWithoutShadows: %d\n", error);
error = 0;
}
}



// FPS
frame++;
time=glutGet(GLUT_ELAPSED_TIME);

if (time - timebase > 1000) {
printf("FPS:%4.2f\n", frame*1000.0/(time-timebase));
timebase = time;
frame = 0;
}

// Reset to draw again
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);

// ++ ---------------------------------------------------------------------------------------------------- ++ //
// First step for shadows
glPushAttrib(GL_ALL_ATTRIB_BITS);
_shadow->drawFromLight(_sun->getPosition());

// Draw the drawables the first time
for(std::list<Drawable*>::iterator it = _drawables.begin(); it != _drawables.end(); it++)
{
(*it)->draw();
}


// ++ ---------------------------------------------------------------------------------------------------- ++ //
// Second step for shadows
_shadow->drawWithShadows(_windowWidth, _windowHeight, _cPosition , _cView, _cUp, _positionY);
_sun->shadowLight();

// Draw the drawables the second time with shadows
for(std::list<Drawable*>::iterator it = _drawables.begin(); it != _drawables.end(); it++)
{
(*it)->draw();
}

// ++ ---------------------------------------------------------------------------------------------------- ++ //
// Second step for shadows
glPushAttrib(GL_ALL_ATTRIB_BITS);
_sun->brightLight();
_shadow->drawWithoutShadows();

// Skybox
//_skybox->draw();


// Draw the drawables the third time with shadows
for(std::list<Drawable*>::iterator it = _drawables.begin(); it != _drawables.end(); it++)
{
(*it)->draw();
}

glPopAttrib();

// Water, grass
//_water->draw();
//_grass->draw();

//_shadow->debug();

// Light out
glDisable(GL_LIGHT0); glDisable(GL_LIGHTING);

// Draw and clear Buffer
glutSwapBuffers();

// Check for Error
GLenum error = glGetError();
if(error == GL_INVALID_OPERATION)
{
printf("Error occured in Viewer: %d\n", error);
error = 0;
}


The sun class only sets the light intesity and holds the position of the light. MyMatrix multiplys the matrices correct.

P.S. I know i should use Shaders for this topic, but it is my first project and i started with the fixed pipeline.

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The lightposition is on (0, 200, 0) and the cube is on (0, 30, 0). The plane under the cube is from (-100,0, -100) to (100, 0, 100). So the shadow should be under the cube.
[attachment=4448:screen.png]

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[color="#0000FF"][color="#000000"]try a

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);


on the shadow tex's

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ok, leave it there, its necessary.

now try to upload some random memory garbage as shadow map texture. it should give you some strange result. lets see if the cmp is working.

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This three lines should do a rnd garbage upload or?
glBindTexture(GL_TEXTURE_2D, _depthTextureId);
GLfloat* buffer = new GLfloat[shadowMapSize * shadowMapSize];
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT24, shadowMapSize, shadowMapSize, 0, GL_DEPTH_COMPONENT, GL_FLOAT, buffer);

The result is a black line through the picture, so i think its no rnd garbage.
[attachment=4450:screen.png]

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Switch to srand timer and try to run through a (rand()%10000000)/1000.0 on your memory area.

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Ok, the result ist the same as in the first picture. (Most of the time, sometimes, there are lines as in picture two)

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Mhh, that is the code for the matrix:
The matrix multiplikation

MyMatrix MyMatrix::operator*(MyMatrix& mat)
{
MyMatrix dummy;

dummy._matrix[0] = _matrix[0] * mat._matrix[0] + _matrix[1] * mat._matrix[4] + _matrix[2] * mat._matrix[8] + _matrix[3] * mat._matrix[12];
dummy._matrix[1] = _matrix[0] * mat._matrix[1] + _matrix[1] * mat._matrix[5] + _matrix[2] * mat._matrix[9] + _matrix[3] * mat._matrix[13];
dummy._matrix[2] = _matrix[0] * mat._matrix[2] + _matrix[1] * mat._matrix[6] + _matrix[2] * mat._matrix[10] + _matrix[3] * mat._matrix[14];
dummy._matrix[3] = _matrix[0] * mat._matrix[3] + _matrix[1] * mat._matrix[7] + _matrix[2] * mat._matrix[11] + _matrix[3] * mat._matrix[15];

dummy._matrix[4] = _matrix[4] * mat._matrix[0] + _matrix[5] * mat._matrix[4] + _matrix[6] * mat._matrix[8] + _matrix[7] * mat._matrix[12];
dummy._matrix[5] = _matrix[4] * mat._matrix[1] + _matrix[5] * mat._matrix[5] + _matrix[6] * mat._matrix[9] + _matrix[7] * mat._matrix[13];
dummy._matrix[6] = _matrix[4] * mat._matrix[2] + _matrix[5] * mat._matrix[6] + _matrix[6] * mat._matrix[10] + _matrix[7] * mat._matrix[14];
dummy._matrix[7] = _matrix[4] * mat._matrix[3] + _matrix[5] * mat._matrix[7] + _matrix[6] * mat._matrix[11] + _matrix[7] * mat._matrix[15];

dummy._matrix[8] = _matrix[8] * mat._matrix[0] + _matrix[9] * mat._matrix[4] + _matrix[10] * mat._matrix[8] + _matrix[11] * mat._matrix[12];
dummy._matrix[9] = _matrix[8] * mat._matrix[1] + _matrix[9] * mat._matrix[5] + _matrix[10] * mat._matrix[9] + _matrix[11] * mat._matrix[13];
dummy._matrix[10] = _matrix[8] * mat._matrix[2] + _matrix[9] * mat._matrix[6] + _matrix[10] * mat._matrix[10] + _matrix[11] * mat._matrix[14];
dummy._matrix[11] = _matrix[8] * mat._matrix[3] + _matrix[9] * mat._matrix[7] + _matrix[10] * mat._matrix[11] + _matrix[11] * mat._matrix[15];

dummy._matrix[12] = _matrix[12] * mat._matrix[0] + _matrix[13] * mat._matrix[4] + _matrix[14] * mat._matrix[8] + _matrix[15] * mat._matrix[12];
dummy._matrix[13] = _matrix[12] * mat._matrix[1] + _matrix[13] * mat._matrix[5] + _matrix[14] * mat._matrix[9] + _matrix[15] * mat._matrix[13];
dummy._matrix[14] = _matrix[12] * mat._matrix[2] + _matrix[13] * mat._matrix[6] + _matrix[14] * mat._matrix[10] + _matrix[15] * mat._matrix[14];
dummy._matrix[15] = _matrix[12] * mat._matrix[3] + _matrix[13] * mat._matrix[7] + _matrix[14] * mat._matrix[11] + _matrix[15] * mat._matrix[15];

return dummy;
}


And with this code i save the lightmatrix and projectionmatrix:

// Init matrices
glPushMatrix();
glLoadIdentity();
gluPerspective(60.0f, 1.0f, 0.1f, lightPosition.y + 10);
glGetFloatv(GL_MODELVIEW_MATRIX, _projectionMatrix);
glPopMatrix();

glPushMatrix();
glLoadIdentity();
gluLookAt(lightPosition.x, lightPosition.y, lightPosition.z,
lightPosition.x, 0, lightPosition.z,
0, 0, 1.0f);
glGetFloatv(GL_MODELVIEW_MATRIX, _lightviewMatrix);
glPopMatrix();


And in drawWithoutShadows i multiply the three matrices:

MyMatrix dummy;
dummy = MyMatrix(bias) * MyMatrix(_projectionMatrix) * MyMatrix(_lightviewMatrix);

const GLfloat first[4] = {dummy[0], dummy[4], dummy[8], dummy[12]};
const GLfloat second[4] = {dummy[1], dummy[5], dummy[9], dummy[13]};
const GLfloat third[4] = {dummy[2], dummy[6], dummy[10], dummy[14]};
const GLfloat fourth[4] = {dummy[3], dummy[7], dummy[11], dummy[15]};


First, second, third and fourth are the arguments for glTexGenfv.
So i dont know why it is bad.

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You see lines instead of ,,white-noise'' while you switched to random image. This means that your shadow map being projected badly.

i suggest you to copy a correctly working matrix code from a working shadow map tutorial, then insert it to your code.

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Nice, you are my hero!

The shadow for the cube is now perfect :-)

So the next step is to load the real landscape with my "beatiful" trees. But the result is not very impressive :-/
[attachment=4452:screen.png]

In theory the shadows are working with the cube and plane. But the trees should also make shadows, right?

If i look under the landscape, you see this picture:
[attachment=4453:screen.png]

And i have one more problem: Shadows and texture? My landscape is in normal mode multitextured, but when i draw with shadows, the shadows disappear and only the texture and the detailtexture is visible. Is there a solution?

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Ok, i have solved the problem. A few tries with glPolygonOffset(4.3f, 3.1f); and no black fragments are left.
The texturing is also solved. The problem was, that my OpenGL/graficcard only supports 4 texture units.

Great thanks for your help, Geri!

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You are welcome! ;)

At the moment, almost all drivers reporting 4 units.
But with some, in reality, you can simply ignore that fact, and you can adress 8 or even 32.

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