multiple shaders , rendertargts, bad result

OpenGL OpenGL: Basic Coding
1

Hello,

i have a strange result when combining shaders. I loaded two shaders.
A perpixel lightning and a glow-shader. Seperatly both are working.
If I only perform the perpixel lightning it works, and if i only perform
the glow shader it works as well.
But when i try to combine those shaders something goes wrong.
I use the glutSolidTeapot in my example. Applying only one shader
(perpixel light, or glow) on the teapot i can rotate and move it.
Applying these two effects i cant rotate the teapot. I only see the
teapot pretty close on the top.

please have a look at the draw method

	static GLenum mrt[] = {GL_COLOR_ATTACHMENT0_EXT, GL_COLOR_ATTACHMENT2_EXT};
	RTT.BeginMRT(2, mrt);	// render original teapot in target 0 and 2
		glPolygonMode( GL_FRONT_AND_BACK, GL_FILL);				
		shader2.SetParameterModelViewProjectionMatrix(CShaderObject::VERTEX,"modelViewProj");
		shader2.SetParameterModelViewMatrixInv(CShaderObject::VERTEX,"modelViewInv");
		shader2.SetParameterFloat3v(CShaderObject::VERTEX,"lightPosition",m_Camera.GetCameraPosition().Array());
		shader2.SetParameterFloat3v(CShaderObject::VERTEX,"eyePosition",m_Camera.GetCameraPosition().Array());

		shader2.Begin();
		//glColor3f(0.95,0.57,0.25);
		::glutSolidTeapot(1.0);
		shader1.End();		
	RTT.End();

	RTT.Begin(1);
		glPolygonMode( GL_FRONT_AND_BACK, GL_FILL);
		cgfx.CgFxSetupSampler("SrcSampler",RTT.GetTextureID(0));
		cgfx.CgFxBegin("pass0");
		RTT.DrawFullscreenQuad();
		cgfx.CgFxEnd();
	RTT.End();

	RTT.Begin(0);
		glPolygonMode( GL_FRONT_AND_BACK, GL_FILL);
		cgfx.CgFxSetupSampler("SrcSampler",RTT.GetTextureID(1));
		cgfx.CgFxBegin("pass1");
		RTT.DrawFullscreenQuad();
		cgfx.CgFxEnd();
	RTT.End();

		// draw teapot texture
		RTT.EnableGLBlendColor();
		glPolygonMode( GL_FRONT_AND_BACK, GL_FILL);
		cgfx.CgFxSetupSampler("SrcSampler",RTT.GetTextureID(2));
		cgfx.CgFxBegin("pass3");
		RTT.DrawFullscreenQuad();
		cgfx.CgFxEnd();

		// glow texture
		glPolygonMode( GL_FRONT_AND_BACK, GL_FILL);		
		cgfx.CgFxSetupSampler("TmpSampler",RTT.GetTextureID(0));
		cgfx.CgFxBegin("pass2");
		RTT.DrawFullscreenQuad();
		cgfx.CgFxEnd();
		RTT.DisableGLBlendColor();

RTT.Begin()

	////////////////////////////////////////
	// unbind texture
	////////////////////////////////////////
	glBindTexture(GL_TEXTURE_2D, 0);
	////////////////////////////////////////
	// bind framebuffer
	////////////////////////////////////////
	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_Framebuffer);
	////////////////////////////////////////
	// bind renderbuffer
	////////////////////////////////////////
	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_Framebuffer);
	////////////////////////////////////////
	// save current attribs
	////////////////////////////////////////	
	glPushAttrib(SaveAttrib); 
	////////////////////////////////////////
	// align viewport
	////////////////////////////////////////
	glViewport(0, 0, m_uiWidth, m_uiHeight);
		////////////////////////////////////////
	// set active attachment (target)
	////////////////////////////////////////
	glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT+Target);
	////////////////////////////////////////
	// clear buffers
	////////////////////////////////////////
	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);	
	////////////////////////////////////////
	// fill cleared buffer with values
	////////////////////////////////////////		
	glClearColor(0,0,0,0);

RTT.End()

	////////////////////////////////////////
	// unbind framebuffer
	////////////////////////////////////////
	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
	////////////////////////////////////////
	// pop attribs
	////////////////////////////////////////
	glPopAttrib();

I guess it has something to do with matrix transformation. But I dont understand how it could effect the other shader.
I also checked out if the glow shader is the reason for my problem, but it isnt. I wrote a simple passthrough shader.
And its the same result. Perpixel lightning + passthrough = wrong result. Teapot is not moving.

here are the links to pictures showing you what im talking about
http://rapidshare.com/files/222047298/glow.jpg
http://rapidshare.com/files/222047562/perpixel.jpg
http://rapidshare.com/files/222047694/perpixel_and_glow.jpg

Any ideas ?

thanks,
cmos

2

some of your codes made me a little confused :


shader2.Begin();
//glColor3f(0.95,0.57,0.25);
::glutSolidTeapot(1.0);
shader1.End();

begin with ‘shader2’ but end with ‘shader1’?


// bind framebuffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_Framebuffer);

// bind renderbuffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_Framebuffer);

did you really bind ‘Renderbuffer’?

3

Hi there, thanks for your reply. I fixed the appearence of the two glBindFramebufferEXT. Now im binding a framebuffer and a renderbuffer.

So, here is also the updated code. The names of the shaders were confusig. Now shader1 performs the per pixel lightning and shader2 is a simple passthrough shader. So, the result is the same as before.


RTT.Begin(0);
glPolygonMode( GL_FRONT_AND_BACK,
GL_FILL);						shader1.SetParameterModelViewProjectionMatrix(CShaderObject::VERTEX,"modelViewProj");		shader1.SetParameterModelViewMatrixInv(CShaderObject::VERTEX,"modelViewInv");		shader1.SetParameterFloat3v(CShaderObject::VERTEX,"lightPosition",m_Camera.GetCameraPosition().Array());	shader1.SetParameterFloat3v(CShaderObject::VERTEX,"eyePosition",m_Camera.GetCameraPosition().Array());
shader1.Begin();
::glutSolidTeapot(1.0);
shader1.End();		
RTT.End();	

glPolygonMode( GL_FRONT_AND_BACK, GL_FILL);	
shader2.SetParameterSampler(CShaderObject::FRAGMENT,"texture",RTT.GetTextureID(0));
shader2.Begin();
RTT.DrawFullscreenQuad();
shader2.End();

greetings,
cmos

4

Ok, whether there is a bug with the Cg runtime or I did something wrong. It’s workign now.

I sawpped these lines


// pass those first	shader1.SetParameterFloat3v(CShaderObject::VERTEX,"eyePosition",m_Camera.GetCameraPosition().Array());
shader1.SetParameterFloat3v(CShaderObject::VERTEX,"lightPosition",m_Camera.GetCameraPosition().Array());

// matrix last		
shader1.SetParameterModelViewProjectionMatrix(CShaderObject::VERTEX,"modelViewProj");
shader1.SetParameterModelViewMatrixInv(CShaderObject::VERTEX,"modelViewInv");

it should make no different which order passing the uniforms to a shader. but in this case it does. i dont know why.

any suggestions anyway ?

greetings,
cmos

5

i also don’t think the order of passing uniforms is the reason.

i have no idea how you implemented your ‘CShaderObject’ class,
does the ‘shader.SetParameter[…]’ functions equivalent to ‘glUniform[…]’ functions?

i would active the shader program first before passing uniforms to it.


shader2.Begin();
shader2.SetParameterModelViewProjectionMatrix(...);
shader2.SetParameterModelViewMatrixInv(...);
...
shader2.End();

all right, i really have no more ideas about this:)