# Heightmap Confirmation

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I've managed to get the texture on the mesh correctly, however I'm not sure about my normal calculations.. In fact I'm not sure about any of it. I'm trying to build Tri Strips and I really need help on calculating the Normals.I need to calculate the face normals first, which can be done using cross product right ? For example (from the code beneath) va.X = u.X - v.X; va.Y = u.Y - v.Y ; va.Z = u.Z - v.Z ; vb.X = u.X - v.X; vb.Y = u.Y - v.Y ; vb.Z = u.Z - v.Z ; face = crossproduct(va,vb); face = Normalize(facet); Once done, each of the vertex normals is the average of the 6 surrounding faces: glNormal3f(face.X/6,face.Y/6,face.Z/6); ???? for each call to glNormal() ? Do I need to take into account boundary values like edges or borders ? Is this correct ? Kind Regards to you all /////////////////////////////////////////////////////////////////////Ter Gen for (int x = 0; x < MAP_SIZE - 1; x++) { // Draw A Triangle Strip For Each Column Of Our Mesh glBegin(MODE); for (int y = 0; y < MAP_SIZE - 1; y++) { glBindTexture(GL_TEXTURE_2D, texture[0]); float_x = (float) x /MAP_SIZE-1; float_y = (float) y /MAP_SIZE-1; float_xb = (float) (x + 1) / MAP_SIZE-1; float_yb = (float) (y + 1) / MAP_SIZE-1; u.X = mesh[x][y][0];//vertex 1 u.Y = mesh[x][y][1]; u.Z = mesh[x][y][2]; v.X = mesh[x+1][y][0];//vertex 2 v.Y = mesh[x+1][y][1]; v.Z = mesh[x+1][y][2]; u.X = mesh[x][y+1][0];//vertex 3 u.Y = mesh[x][y+1][1]; u.Z = mesh[x][y+1][2]; v.X = mesh[x+1][y+1][0];//vertex 4 v.Y = mesh[x+1][y+1][1]; v.Z = mesh[x+1][y+1][2]; n = crossproduct(u,v); n = Normalize(n); glTexCoord2f(float_x, float_y); glNormal3f(n.X,n.Y,n.Z); glVertex3f(mesh[x][y][0], mesh[x][y][1], mesh[x][y][2]); glTexCoord2f(float_xb, float_y); glVertex3f(mesh[x+1][y][0], mesh[x+1][y][1], mesh[x+1][y][2]); glTexCoord2f(float_xb, float_yb); } glEnd(); }

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Strictly speaking, averaging face normals is not correct because the resulting vector does not have a length of 1. However, it is fast and the results may be good enough. Because a vertex normal is only an approximation, there are several ways to compute it. This article does a good job of explaining and comparing the different methods: Normal Computations for Heightfield Lighting.

There are different ways of handling edges. It may depend on what is beyond the edge.

Finally... for now, while you are drawing brute force using immediate mode, stick with triangle strips. However, once you move to vertex arrays, you should use a single triangle list instead of a bunch of triangle strips until you get everything working well. Triangle lists are easier to deal with and you will find that drawing one big triangle list is faster than drawing MAP_SIZE triangle strips. There is a way to draw a grid using a single triangle strip, but it is complicated so I would hold off on that optimization until you get things working.

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