CODEWITHSUNDEEP
openglshadercg
spacevillain
spacevillain

Reputation: 1336

Shader and opengl transformations

When i add shaders (in cg) to my opengl program all the local transformations (glRotatef, glTranslatef and glScalef between glPushMatrix and glPopMatrix) stop working. Transforms outside push/pop still working though. So what might be the problem here?

update: I have a rotating cube in the center of the scene:

glPushMatrix();
glRotatef(angle, 1, 0, 0);
drawBox();
glPopMatrix();

and after that i send worldview and worldviewprojection matrices to shader:

cgGLSetStateMatrixParameter(
    myCgVertexParam_modelViewProj,
    CG_GL_MODELVIEW_PROJECTION_MATRIX,
    CG_GL_MATRIX_IDENTITY
);

cgGLSetStateMatrixParameter(
    myCgVertexParam_modelView,
    CG_GL_MODELVIEW_MATRIX,
    CG_GL_MATRIX_IDENTITY
);

Vertex shader code:

void C9E2v_fog(float4 position    : POSITION,
               float4 color       : COLOR,

            out float4 oPosition    : POSITION,
            out float4 oColor       : COLOR,
            out float  fogExponent  : TEXCOORD1,

        uniform float    fogDensity,  // Based on log2
        uniform float4x4 modelViewProj : MODELVIEW_PROJECTION_MATRIX,
        uniform float4x4 modelView : MODELVIEW_MATRIX)
{   
  // Assume nonprojective modelview matrix
  float3 eyePosition = mul(modelView, position).xyz;
  float fogDistance  = length(eyePosition);
  fogExponent  = fogDistance * fogDensity;
  oPosition    = mul(modelViewProj, position);

  //oDecalCoords = decalCoords;
  oColor       = color;
}

So in the end cube doesnt rotate, but if i do write (no push/pop)

glRotatef(angle, 1, 0, 0);
drawBox();

everything works fine. How do i fix that?

Upvotes: 2

Views: 2445

Answers (1)

erjot
erjot

Reputation: 1412

You can use either fixed function pipeline or programmable one. Since you switched to shaders, fixed function pipeline "stopped working". To switch back you need to glUseProgram(0). And you need to send those local transformations to the shader.

Upvotes: 3

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