RE: [Algorithms] Terrain Normals

[Pallister, K. <kim...@in...>]

I had similar problems that I assumed were just the gouraud shading, until I
drew the normals, and then could see the problem clearly (a code bug).

Draw the normals. Not hard, and it will help you.



Kim Pallister

We will find a way or we will make one.
                     - Hannibal


> -----Original Message-----
> From: Pai-Hung Chen [mailto:pa...@ac...]
> Sent: Sunday, August 13, 2000 11:23 PM
> To: gda...@li...
> Subject: [Algorithms] Terrain Normals
> 
> 
> Hi,
> 
> I've written a routine to read a bitmap heightfield and 
> construct a terrain
> mesh from it.  I partition each set of four pixels into two 
> triangles along
> the upper-right-to-lower-left diagonal line.  Therefore, for 
> example, a 128
> x 128 bitmap will produce (128-1) x (128-1) x 2 = 32258 
> triangles using my
> method.  For each triangle I caculate its unit face normal.  
> For each vertex
> of a triangle, I calculate its vertex normal by adding and 
> averaging the
> face normals of all triangles that share the vertex (in my 
> case a vertex can
> be shared by at most six triangles and at least one triganle) and then
> normalize the averaged normal, which is used in redering.  My 
> problem is
> that there are some *horizontal dimmed banding* effects along 
> the triangle
> edges of the mesh when rendering in D3D with light cast on 
> it.  Also, there
> are very visible dimmed seams between triangles when light is 
> cast on it.
> All these artifacts seem to manifest only when light is cast 
> in large angles
> (i.e. not directly).  Is it because the arrangement of 
> triangles in my mesh
> is too *uniform* (actually they are extremely uniform)?  Or is my
> calculation of vertex normals incorrect?
> 
> Thanks in advance,
> 
> Pai-Hung Chen
> 
> 
> 
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