if i want e.g. to reflect a scene in water, i scale about (1, -1, 1), setup a clipping plane with a normal vector pointing up and offset the scene.
now i'm trying to figure out how i have to setup the scale matrix and the clipping plane to reflect a scene about an arbitrary plane, for arbitrarily placed and oriented mirrors.
does someone know how to do that? thanks
I haven't done this personally, but I'd start with a definition of a reflection matrix here:
http://en.wikipedia.org/wiki/Transformation_matrix
So you wouldn't be using the scale transformation but using something like glMultMatrixd on the GL_MODELVIEW_MATRIX.
If your plane isn't through the origin then you'd have to apply a translation after the reflection.
Look at glhGeneralPlanarMirrorf_1, glhGeneralPlanarMirrorf_2
in the header file.
http://www.geocities.com/vmelkon/glhlibrary.html
It's open source so you can adapt it to your particular way of transforming your mirror to eye space.
------------------------------
Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
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