Correcting Lighting in Stencil Reflections
- by Reanimation
I'm just playing around with OpenGL seeing how different methods of making shadows and reflections work.
I've been following this tutorial which describes using GLUT_STENCIL's and MASK's to create a reasonable interpretation of a reflection.
Following that and a bit of tweaking to get things to work, I've come up with the code below.
Unfortunately, the lighting isn't correct when the reflection is created.
glPushMatrix();
plane(); //draw plane that reflection appears on
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS, 1, 0xFFFFFFFF);
glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
plane(); //draw plane that acts as clipping area for reflection
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_TRUE);
glStencilFunc(GL_EQUAL, 1, 0xFFFFFFFF);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glDisable(GL_DEPTH_TEST);
glPushMatrix();
glScalef(1.0f, -1.0f, 1.0f);
glTranslatef(0,2,0);
glRotatef(180,0,1,0);
sphere(radius, spherePos); //draw object that you want to have a reflection
glPopMatrix();
glEnable(GL_DEPTH_TEST);
glDisable(GL_STENCIL_TEST);
sphere(radius, spherePos); //draw object that creates reflection
glPopMatrix();
It looked really cool to start with, then I noticed that the light in the reflection isn't correct.
I'm not sure that it's even a simple fix because effectively the reflection is also a sphere but I thought I'd ask here none-the-less.
I've tried various rotations (seen above the first time the sphere is drawn) but it doesn't seem to work. I figure it needs to rotate around the Y and Z axis but that's not correct.
Have I implemented the rotation wrong or is there a way to correct the lighting?
