[Request for help] Texture mapping a subdivided icosahedron

IainC · 2002-09-28T11:00:04

Hi all, I'm using a subdivided icosahedron as an approximation to a sphere; I'm doing it this way instead of using a quadric because I'm going to want to deform the sphere and this method gives me uniform point distribution. The technique is described in example 2-13 of the Red Book. The problem I'm having is texturing the thing. I want to be able to pass a function the normal of the current point and have it pass back appropriate UV coords. // ******************** DEFINES ******************** #define X_BASE 0.525731112119133606f #define Z_BASE 0.850650808352039932f // ******************** STRUCTS ******************** struct Vector3f { GLfloat x, y, z; void Set(GLfloat m_x, GLfloat m_y, GLfloat m_z) { x = m_x; y = m_y; z = m_z; } }; // ******************** CLASS DEFINITION ******************** class Icosahedron { public: Icosahedron(); ~Icosahedron(); void Init(GLfloat m_radius, int subdivisions); void Render(); private: void Normalize(float v[3]); void DrawTriangle(float *v1, float *v2, float *v3); void Subdivide(float *v1, float *v2, float *v3, long depth); void GetTextureCoord(ASEVector3f *normal, float *targetU, float *targetV); GLuint displayList; GLfloat radius; }; // ******************** CLASS IMPLEMENTATION ******************** GLfloat vdata[12][3] = { {-X_BASE,0.0,Z_BASE},{X_BASE,0.0,Z_BASE},{-X_BASE,0.0,-Z_BASE},{X_BASE,0.0,-Z_BASE}, {0.0,Z_BASE,X_BASE},{0.0,Z_BASE,-X_BASE},{0.0,-Z_BASE,X_BASE},{0.0,-Z_BASE,-X_BASE}, {Z_BASE,X_BASE,0.0},{-Z_BASE,X_BASE,0.0},{Z_BASE,-X_BASE,0.0},{-Z_BASE,-X_BASE,0.0}}; GLuint tindices[20][3] = { {1,4,0},{4,9,0},{4,5,9},{8,5,4},{1,8,4}, {1,10,8},{10,3,8},{8,3,5},{3,2,5},{3,7,2}, {3,10,7},{10,6,7},{6,11,7},{6,0,11},{6,1,0}, {10,1,6},{11,0,9},{2,11,9},{5,2,9},{11,2,7}}; Icosahedron::Icosahedron() { } Icosahedron::~Icosahedron() { } void Icosahedron::Init(GLfloat m_radius, int subdivisions) { radius = m_radius; displayList = glGenLists(1); glNewList(displayList, GL_COMPILE); for (int i = 0; i < 20; i++) { Subdivide(&vdata[tindices[i][0]][0], &vdata[tindices[i][1]][0], &vdata[tindices[i][2]][0], subdivisions); } glEndList(); } void Icosahedron::Render() { glScalef(radius, radius, radius); glCallList(displayList); } void Icosahedron::DrawTriangle(float *v1, float *v2, float *v3) { Vector3f point; GLfloat texU, texV; glBegin(GL_TRIANGLES); point.Set (v1[0], v1[1], v1[2]); glNormal3f (point.x, point.y, point.z); // (Points are already normalised) GetTextureCoord (&point, &texU, &texV); glTexCoord2f(texU, texV); glVertex3f (point.x, point.y, point.z); point.Set (v2[0], v2[1], v2[2]); glNormal3f (point.x, point.y, point.z); GetTextureCoord (&point, &texU, &texV); glTexCoord2f(texU, texV); glVertex3f (point.x, point.y, point.z); point.Set (v3[0], v3[1], v3[2]); glNormal3f (point.x, point.y, point.z); GetTextureCoord (&point, &texU, &texV); glTexCoord2f(texU, texV); glVertex3f (point.x, point.y, point.z); glEnd(); } void Icosahedron::GetTextureCoord(ASEVector3f *normal, float *targetU, float *targetV) { // **************************************** // **************************************** // IT'S THIS FUNCTION I CAN'T GET TO WORK!! // **************************************** // **************************************** } void Icosahedron::Normalize(float v[3]) { GLfloat d = (float)sqrt(v[0]*v[0]+v[1]*v[1]+v[2]*v[2]); if (d == 0.0) return; v[0] /= d; v[1] /= d; v[2] /= d; } void Icosahedron::Subdivide(float *v1, float *v2, float *v3, long depth) { GLfloat v12[3], v23[3], v31[3]; GLint i; if (depth == 0) { DrawTriangle(v1, v2, v3); return; } for (i = 0; i < 3; i++) { v12[i] = v1[i]+v2[i]; v23[i] = v2[i]+v3[i]; v31[i] = v3[i]+v1[i]; } Normalize(v12); Normalize(v23); Normalize(v31); Subdivide(v1, v12, v31, depth-1); Subdivide(v2, v23, v12, depth-1); Subdivide(v3, v31, v23, depth-1); Subdivide(v12, v23, v31, depth-1); } Any thoughts? Thanks in advance for any help anyone can provide! Brgrds, IainC www.coldcity.com code, pics, life Grr I can't make the source tag keep my formatting... [edited by - IainC on September 27, 2002 6:00:20 AM]

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Started by IainC September 27, 2002 04:55 AM

21 comments, last by IainC 22 years, 5 months ago

IainC

Author

127

September 28, 2002 10:40 AM

Enigma,

My solution was to count the number of faces used for a given level of subdivision, and thus be able to tell when I was outputing a face if it lay on the seam; I think it''s slightly cheaper than yours, but still a fairly ugly hack

Anyway, all sorted now! The pic below shows the final sphere with two different LODs - you can see the texture maps perfectly on both.

Thanks for all your help - I owe you a pint if you''re ever in Southampton

[size="2"]www.coldcity.com code, art, life

Enigma

1,410

September 28, 2002 10:52 AM

You''re not going to believe this but...
I''m just about to start my third year at university in.. you guessed it, Southampton!

Enigma

IainC

Author

127

September 28, 2002 11:00 AM

LOL! Damn, the UK''s a small place :D

I''m on the Isle Of Skye just now but soon moving to Southampton to be with my GF - and that drink will be there if you want it

)

The reason I said Southampton instead of Skye is cos your average person has more chance of turning up in the former!

[size="2"]www.coldcity.com code, art, life

[Request for help] Texture mapping a subdivided icosahedron

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[Request for help] Texture mapping a subdivided icosahedron

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