Hi, To make phong shading using shaders(in GLSL), I have to pass the the light position to the vertex shader, But the position of the vertex will be in eyespace (after multiplication with the ModelView matrix). So I need the light position in eye-space as well. Which is the best way of obtaining the correct light position? Either I need the vertex position to be in world space, I do in this way:
mat4 modelMatrix = osg_ViewMatrixInverse* gl_ModelViewMatrix ; WorldPos=modelMatrix * gl_Vertex; mat3 normalmatrix=mat3(modelMatrix); WorldNrm=normalize(normalmatrix * gl_Normal); though it works well to get the world space coordinate of each vertex, but to compute specular of object I have to know the eye position, since we are not in eye coordinates the eye postion is no longer (0,0,0), must the eye coordinate be passed by uniform? Or I need the light position in eye space. I try to translate the light position into eye coordinate in this way: Pos_light0 = osg_ViewMatrix *light0_pos ; or Pos_light0 = light0_pos * osg_ViewMatrix ; but it seems not work. What are the general strategy for this problem? Thanks very much! Julie 2008-09-09
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