98 lines
2.7 KiB
C
98 lines
2.7 KiB
C
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#include "space.h"
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// From 'psyq/addons/graphics/ZIMEN/CLIP.C'
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void worldToScreen( VECTOR * worldPos, VECTOR * screenPos ) {
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int distToScreen; // corresponds to FOV
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MATRIX curRot; // current rotation matrix
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// Get current matrix and projection */
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distToScreen = ReadGeomScreen();
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ReadRotMatrix(&curRot);
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// Get Rotation, Translation coordinates, apply perspective correction
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// Muliply world coordinates vector by current rotation matrix, store in screenPos
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ApplyMatrixLV(&curRot, worldPos, screenPos);
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// Get world translation vectors from rot and add to screenPos vx, vy, vz
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applyVector(screenPos, curRot.t[0], curRot.t[1], curRot.t[2], +=);
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// Correct perspective
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screenPos -> vx = screenPos -> vx * distToScreen / ( screenPos -> vz + 1 ) ; // Add 1 to avoid division by 0
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screenPos -> vy = screenPos -> vy * distToScreen / ( screenPos -> vz + 1 ) ;
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screenPos -> vz = distToScreen ;
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};
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void screenToWorld( VECTOR * screenPos, VECTOR * worldPos ) {
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int distToScreen; // corresponds to FOV
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MATRIX curRot, invRot; // current rotation matrix, transpose matrix
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VECTOR Trans; // working translation vector
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// Get current matrix and projection
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distToScreen = ReadGeomScreen();
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ReadRotMatrix( &curRot );
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PushMatrix(); // Store matrix on the stack (slow!)
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//// worldTrans = invRot * (screenPos - Rot.t)
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// Get world translation
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Trans.vx = screenPos->vx - curRot.t[0]; // Substract world translation from screenpos
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Trans.vy = screenPos->vy - curRot.t[1];
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Trans.vz = screenPos->vz - curRot.t[2];
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// We want the inverse of the current rotation matrix.
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//
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// Inverse matrix : M^-1 = 1 / detM * T(M)
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// We know that the determinant of a rotation matrix is 1, thus:
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// M^-1 = T(M)
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//
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// Get transpose of current rotation matrix
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// > The transpose of a matrix is a new matrix whose rows are the columns of the original.
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// https://www.quora.com/What-is-the-geometric-interpretation-of-the-transpose-of-a-matrix
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TransposeMatrix( &curRot, &invRot );
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// Multiply the transpose of current rotation matrix by the current translation vector
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ApplyMatrixLV( &invRot, &Trans, worldPos );
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// Get original rotation matrix back
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PopMatrix();
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};
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int cliptest3( short *v1 ) {
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if( v1[0]<0 && v1[2]<0 && v1[4]<0 ) return 0;
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if( v1[1]<0 && v1[3]<0 && v1[5]<0 ) return 0;
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if( v1[0] > SCREENXRES && v1[2] > SCREENXRES && v1[4] > SCREENXRES) return 0;
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if( v1[1] > SCREENYRES && v1[3] > SCREENYRES && v1[5] > SCREENYRES) return 0;
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return 1;
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};
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