CODEWITHSUNDEEP
opengllight
seb
seb

Reputation: 2134

OpenGL lighting with glOrtho

So I have a 3D object that I'm drawing with the following light:

    GLfloat light_diffuse[] = {1.0, 1.0, 1.0, 0.9};  /* White light. */
GLfloat light_position[] = {300.0, 300.0, 300.0, 0.0};  
glShadeModel(GL_SMOOTH);
glEnable(GL_COLOR_MATERIAL);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glEnable(GL_LIGHT0);
glEnable(GL_LIGHTING);

My object is illuminated as I expect when I draw it in a "normal" context (i.e. no glOrtho).

However, I'm working on the orthogonal projections of the object and use glOrtho for that purpose (on the ModelView matrix). I initialize the light after the glOrtho call, then draw the object in the exact same way as I did in the case that worked (the 3D case). But for some reason, the lighting does not work on the orthogonal projections, i.e. once I did the glOrtho call.

This is not a problem with normals since it works in the 3D case. I'm guessing that with the glOrtho call, everything gets pressed together on a thin layer, which explains why the light doesn't behave as expected... but honestly, I have not experience with lighting so this might be wrong.

Anyone knows what's going on?

Upvotes: 3

Views: 644

Answers (1)

datenwolf
datenwolf

Reputation: 162164

Lighting happens in eye space, i.e. before the projection is applied at all. You probably use the transformations matrices in a wrong way. glOrtho, glFrustung or gluPerspective go into GL_PROJECTION matrix, gluLookAt and other camera placement stuff go into GL_MODELVIEW.

Upvotes: 1

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