Do OpenGL texture coordinates have to be within range 0-1

Question

For example, if I am using glTexCoord3f(GLfloat s,GLfloat t,GLfloat r), paramesters s, t, r are supposed to be within the range of 0.0f and 1.0f. But I am wonder whether it will be okay for us to set some values which are beyond this range?

The motivation for doing this is that if I am trying to visualize the cross section of a cube as shown in the following image. The red rectangle 'abcd' is the cross section I am trying to visualize. But I notice that the coordinates of the green rectangle 'ABCD' is a lot easier to get (especially when the plane is not perpendicular to any axis).

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I just give that a try. It seems that there is no problem what so ever. But I am still a little bit worry about that though. I don't know whether it is good practice to do so. Whether this is supported by all sort of graphic cards?

Answer 1

OpenGL texture coordiates may be arbitrary values. They will however be clamped, or repeated/wrapped into the range 0…1 depending on the texture coordinate wrap or clamp settings.

Also some texture targets treat texture coordinates differently. GL_TEXTURE_xD behave as one would expect. GL_TEXTURE_CUBE_MAP takes the texture coordinate to be a direction vector. GL_TEXTURE_2D_ARRAY treats the S and T components as usual, but the R component as a layer index. GL_TEXTURE_RECTANGLE treats the texture coordinates as pixel indices into the texture image.