Cube made of Triangles shading problem
Posted Sunday, 26 September, 2010 - 18:32 by tomster1996 inI have a cube made of triangles but when I apply lighting, the triangles that are next to each other seem to have opposite normals. However the normals of the triangles on the same face of the cube are the same.
What might the problem be?
Here's the file containing the coordinates of the vertexs.
SIDE1 triangle1 v1 -5 -5 0 v2 5 -5 0 v3 -5 -5 10 triangle2 v1 5 -5 0 v2 5 -5 10 v3 -5 -5 10 SIDE2 triangle1 v1 -5 5 0 v2 5 5 0 v3 -5 5 10 triangle2 v1 5 5 10 v2 5 5 0 v3 -5 5 10 SIDE3 triangle1 v1 -5 -5 0 v2 -5 -5 10 v3 -5 5 0 triangle2 v1 -5 -5 10 v2 -5 5 0 v3 -5 5 10 SIDE4 triangle1 v1 5 -5 0 v2 5 -5 10 v3 5 5 0 triangle2 v1 5 -5 10 v2 5 5 0 v3 5 5 10 SIDE5 triangle1 v1 -5 -5 10 v2 5 -5 10 v3 5 5 10 triangle2 v1 5 5 10 v2 -5 5 10 v3 -5 -5 10 SIDE6 triangle1 v1 -5 -5 0 v2 5 -5 0 v3 5 5 0 triangle2 v1 5 5 0 v2 -5 5 0 v3 -5 -5 0
Here's the file containing the normals of each triangle.
SIDE1 n1 0 -1 0 n2 0 -1 0 SIDE2 n1 0 1 0 n2 0 1 0 SIDE3 n1 -1 0 0 n2 -1 0 0 SIDE4 n1 1 0 0 n2 1 0 0 SIDE3 n1 -1 0 0 n2 -1 0 0 SIDE4 n1 1 0 0 n2 1 0 0 SIDE5 n1 0 0 1 n2 0 0 1 SIDE6 n1 0 0 -1 n2 0 0 -1
Comments
Re: Cube made of Triangles shading problem
One easy way to debug this: grab a pencil and paper, choose a suitable coordinate system and plot your triangles one after the other. The errors will show quickly that way.
Re: Cube made of Triangles shading problem
Thanks, and can I quickly ask, how do you color the triangles? When i use GL.Color3(System.Drawing.Color.Red), it works fine with the lighting turned off, but if i turn on lighting the triangles stay grey.
Re: Cube made of Triangles shading problem
The orientation of the triangles determines the front/back face, and the two triangles making up a quad face in your code have different orientation each. This only works if twosided lighting is enabled, otherwise assure that the orientation is equal.
Re: Cube made of Triangles shading problem
GL.LightModel(LightModelParameter.LightModelTwoSide, 1);
Does mean two sided lighting is enabled? Whatever the value is in the final parameter of this function, the problem still persists.
Re: Cube made of Triangles shading problem
Does mean two sided lighting is enabled?
Please check some OpenGL resources about what's needed. Usually LightModelTwoSide set to 1 as well as ColorMaterial set to FrontAndBack for the relevant material may be enough.
But, as already posted, get your orientations correct first unless you have a *serious* reason to use inconsistent ones.
Re: Cube made of Triangles shading problem
Once you enable fixed-function lighting, you have to specify light and material parameters, otherwise defaults will be used.
http://www.glprogramming.com/red/chapter05.html