When I render complicated 3D models in OpenGL I use automatic texture coords generation for s,t. In manual case to apply complete texture to object we keep tex coords within [0.0,1.0]. How to keep them within this range in automatic tex coords generation mode? (Its ugly, for a fixed texture, changing 3d model size you get from just a small tex part sticked to it or for bigger sized models the texture becomes repeated all over them)?
Have you tried using the texture coordinate transformation matrix?
No I havent. What is this and how to apply it.
I just do simple texture loading and enable automatic texture coord generation for GL_S, GL_T
supplying appropriate plane equations.
glTexGeni(GL_S,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
glTexGenfv(GL_S,GL_OBJECT_PLANE,splane);
glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
glTexGenfv(GL_T,GL_OBJECT_PLANE,tplane);
glEnable(GL_TEXTURE_GEN_S);
glEnable(GL_TEXTURE_GEN_T);
… then render 3d model.
glMatrixMode
glScale
Dorbie’s suggestion (which is also endash’s suggestion) will work.
However, you can do this yourself by just modifying the planes you put in for texgen.
The plane is a normal (A,B,C) and distance (D). If the diameter of your objects’ bounding radius is X, you want to scale the normal by 1/X. You then should calculate the minimum point Y of your model WRT the (normalized) normal’s direction, and set D to -Y. If your model is centered at the origin, the value of Y is your model’s radius.
Do this to the values for each of the planes you have, before you give them to GL, and all will be well.
Yet a problrm with palnes equations for glTexGen().
Supposing a 2D texture and GL_S GL_T enabled and given an arbitrary shaped model centered at the origin.
- Applying splane[] = {1.0,0.0,0.0,0.0}
tplane[] = {0.0,1.0,0.0,0.0}
we get texture generation for face and back of the model, hence from sides, top and bottom it looks very ugly. - Applying splane[] = {1.0,0.0,0.0,0.0}
tplane[] = {0.0,0.0,1.0,0.0}
we get texture generation for top and bottom of the model, hence from face, back and sides it again looks very ugly.
…and so on
There are no problems if I have surface patch with hight on Y axis then applying 2. equations the texture perfectly applyed on top (its all we need).
But if 3D model of the arbitrary shape (similar to a shpere or cube or conus) how to get simultaneous texture generation for face and back, sides, top and bottom?
If your model is convex, you’ll be better of using cube-maps or sphere-mapping. If it’s not, and you still want to use the automatic texcoord generation you could split your model in various patches based on the normal direction of each triangle and/or occlusions and apply different texgen planes for each patch.
Greetz,
Nico