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POCalculating normals in a triangle mesh
 

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  1. POCalculating normals in a triangle mesh
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    <p>I have drawn a triangle mesh with 10000 vertices(100x100) and it will be a grass ground. I used gldrawelements() for it. I have looked all day and still can't understand how to calculate the normals for this. Does each vertex have its own normals or does each triangle have its own normals? Can someone point me in the right direction on how to edit my code to incorporate normals?</p> <pre><code>struct vertices { GLfloat x; GLfloat y; GLfloat z; }vertices[10000]; GLuint indices[60000]; /* 99..9999 98..9998 ........ 01..9901 00..9900 */ void CreateEnvironment() { int count=0; for (float x=0;x&lt;10.0;x+=.1) { for (float z=0;z&lt;10.0;z+=.1) { vertices[count].x=x; vertices[count].y=0; vertices[count].z=z; count++; } } count=0; for (GLuint a=0;a&lt;99;a++){ for (GLuint b=0;b&lt;99;b++){ GLuint v1=(a*100)+b;indices[count]=v1;count++; GLuint v2=(a*100)+b+1;indices[count]=v2;count++; GLuint v3=(a*100)+b+100;indices[count]=v3;count++; } } count=30000; for (GLuint a=0;a&lt;99;a++){ for (GLuint b=0;b&lt;99;b++){ indices[count]=(a*100)+b+100;count++;//9998 indices[count]=(a*100)+b+1;count++;//9899 indices[count]=(a*100)+b+101;count++;//9999 } } } void ShowEnvironment(){ //ground glPushMatrix(); GLfloat GroundAmbient[]={0.0,0.5,0.0,1.0}; glMaterialfv(GL_FRONT,GL_AMBIENT,GroundAmbient); glEnableClientState(GL_VERTEX_ARRAY); glIndexPointer( GL_UNSIGNED_BYTE, 0, indices ); glVertexPointer(3,GL_FLOAT,0,vertices); glDrawElements(GL_TRIANGLES,60000,GL_UNSIGNED_INT,indices); glDisableClientState(GL_VERTEX_ARRAY); glPopMatrix(); } </code></pre> <p>EDIT 1 Here is the code I have written out. I just used arrays instead of vectors and I stored all of the normals in the struct called normals. It still doesn't work however. I get an unhandled exception at *indices.</p> <pre><code>struct Normals { GLfloat x; GLfloat y; GLfloat z; }normals[20000]; Normals* normal = normals; //***************************************ENVIRONMENT************************************************************************* struct vertices { GLfloat x; GLfloat y; GLfloat z; }vertices[10000]; GLuint indices[59403]; /* 99..9999 98..9998 ........ 01..9901 00..9900 */ void CreateEnvironment() { int count=0; for (float x=0;x&lt;10.0;x+=.1) { for (float z=0;z&lt;10.0;z+=.1) { vertices[count].x=x; vertices[count].y=rand()%2-2;; vertices[count].z=z; count++; } } //calculate normals GLfloat vector1[3];//XYZ GLfloat vector2[3];//XYZ count=0; for (int x=0;x&lt;9900;x+=100){ for (int z=0;z&lt;99;z++){ vector1[0]= vertices[x+z].x-vertices[x+z+1].x;//vector1x vector1[1]= vertices[x+z].y-vertices[x+z+1].y;//vector1y vector1[2]= vertices[x+z].z-vertices[x+z+1].z;//vector1z vector2[0]= vertices[x+z+1].x-vertices[x+z+100].x;//vector2x vector2[1]= vertices[x+z+1].y-vertices[x+z+100].y;//vector2y vector2[2]= vertices[x+z+1].z-vertices[x+z+100].z;//vector2z normals[count].x= vector1[1] * vector2[2]-vector1[2]*vector2[1]; normals[count].y= vector1[2] * vector2[0] - vector1[0] * vector2[2]; normals[count].z= vector1[0] * vector2[1] - vector1[1] * vector2[0];count++; } } count=10000; for (int x=100;x&lt;10000;x+=100){ for (int z=0;z&lt;99;z++){ vector1[0]= vertices[x+z].x-vertices[x+z+1].x;//vector1x -- JUST ARRAYS vector1[1]= vertices[x+z].y-vertices[x+z+1].y;//vector1y vector1[2]= vertices[x+z].z-vertices[x+z+1].z;//vector1z vector2[0]= vertices[x+z+1].x-vertices[x+z-100].x;//vector2x vector2[1]= vertices[x+z+1].y-vertices[x+z-100].y;//vector2y vector2[2]= vertices[x+z+1].z-vertices[x+z-100].z;//vector2z normals[count].x= vector1[1] * vector2[2]-vector1[2]*vector2[1]; normals[count].y= vector1[2] * vector2[0] - vector1[0] * vector2[2]; normals[count].z= vector1[0] * vector2[1] - vector1[1] * vector2[0];count++; } } count=0; for (GLuint a=0;a&lt;99;a++){ for (GLuint b=0;b&lt;99;b++){ GLuint v1=(a*100)+b;indices[count]=v1;count++; GLuint v2=(a*100)+b+1;indices[count]=v2;count++; GLuint v3=(a*100)+b+100;indices[count]=v3;count++; } } count=30000; for (GLuint a=0;a&lt;99;a++){ for (GLuint b=0;b&lt;99;b++){ indices[count]=(a*100)+b+100;count++;//9998 indices[count]=(a*100)+b+1;count++;//9899 indices[count]=(a*100)+b+101;count++;//9999 } } } void ShowEnvironment(){ //ground glPushMatrix(); GLfloat GroundAmbient[]={0.0,0.5,0.0,1.0}; GLfloat GroundDiffuse[]={1.0,0.0,0.0,1.0}; glMaterialfv(GL_FRONT,GL_AMBIENT,GroundAmbient); glMaterialfv(GL_FRONT,GL_DIFFUSE,GroundDiffuse); glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_NORMAL_ARRAY); glNormalPointer( GL_FLOAT, 0, normal); glVertexPointer(3,GL_FLOAT,0,vertices); glDrawElements(GL_TRIANGLES,60000,GL_UNSIGNED_INT,indices); glDisableClientState(GL_VERTEX_ARRAY); glDisableClientState(GL_NORMAL_ARRAY); glPopMatrix(); } //*************************************************************************************************************************** </code></pre>
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    1. COWhat the heck are you doing with that [`glIndexPointer()`](http://www.opengl.org/sdk/docs/man/xhtml/glIndexPointer.xml) call? [Indexed color](http://en.wikipedia.org/wiki/Indexed_color) has nothing to do with the `indices` argument of [`glDrawElements()`](http://www.opengl.org/sdk/docs/man/xhtml/glDrawElements.xml).
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      1. POCalculating normals in a triangle mesh
      1. USgenpfault
    2. COVertices cannot have normals (unless they are an average of face normals for the faces around them). I've never used openGL so I don't know if there's a way to get them simply. I would imagine so, but if you wanted to do it yourself you could always calculate the edge vectors from the vertices and calculate the normals by taking the cross product of two edges (then normalizing to magnitude 1).
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      1. POCalculating normals in a triangle mesh
      1. USDan
    3. COI just edited it. I made some changes to the code but it doesn't compile.
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      1. POCalculating normals in a triangle mesh
      1. USVince
 

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