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| OpenGL transform matrix |
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space warp Member since: 9/17/2006 |
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 Posted - 3/31/2007 9:58:58 AM |
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| I'm making a space-shooter-demo for fun and I have built a matrix that stores rotation and position of the ship. I've tried it and it rotates correctly and everything but when I change the position nothing happens, the ship is still at the origin. I'm using glMultMatrix() for this and I would like to know what format OpenGL uses for the transformation matrix and why I can't move the ship. |
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Yann L Moderator Member since: 2/6/2002 From: Breizh |
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 Posted - 3/31/2007 10:43:55 AM |
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| Since unfortunately we're not psychic, we can't know what is wrong with your matrix without seeing it (ie. the code that generates it). OpenGL uses column major order (by default). A 4x4 matrix looks like this in memory: [0 4 8 12] [1 5 9 13] [2 6 10 14] [3 7 11 15] The upper left 3x3 part represents rotations and scaling (and shearing), the top right 3 element column (12, 13, 14) the translation: [R0 R3 R6 Tx] [R1 R4 R7 Ty] [R2 R5 R8 Tz] [ 0 0 0 1] Now show us the code that generates your matrix, and we can see further. |
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space warp Member since: 9/17/2006 |
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Posted - 3/31/2007 11:04:34 AM |
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It is what you described.double mat[16]; mat[0] = Cell(0,0); mat[4] = Cell(1,0); mat[8] = Cell(2,0); mat[12] = Cell(3,0); mat[1] = Cell(0,1); mat[5] = Cell(1,1); mat[9] = Cell(2,1); mat[13] = Cell(3,1); mat[2] = Cell(0,2); mat[6] = Cell(1,2); mat[10] = Cell(2,2); mat[14] = Cell(3,2); mat[3] = Cell(0,3); mat[7] = Cell(1,3); mat[11] = Cell(2,3); mat[15] = Cell(3,3); glMultMatrixd(mat); Cell(x,y) is a function that multiplies the rotation matrix and the translation matrix so that I get the transformation matrix. double TRMATRIX::Cell(int x, int y) { return rot[0][y] * pos[x][0] + rot[1][y] * pos[x][1] + rot[2][y] * pos[x][2] + rot[3][y] * pos[x][3]; } The rotation matrix looks like this: [R1 R2 R3 0] [R4 R5 R6 0] [R7 R8 R9 0] [0 0 0 1] and the translation matrix looks like this: [1 0 0 X] [0 1 0 Y] [0 0 1 Z] [0 0 0 1] |
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space warp Member since: 9/17/2006 |
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Posted - 3/31/2007 1:17:46 PM |
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| Solved. |
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| All times are ET (US) |
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