Code archives/3D Graphics - Misc/TriMesh
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| Draws the triangles in a mesh, skipping those facing away from the camera. Useful for limited display of simple meshes, anyway... Big thanks to Mark, SSwift and Floyd! UPDATED: Speeded up a lot by inlining everything. Now using Simon Armstrong's AcidLine function for even more speed :) | |||||
; ----------------------------------------------------------------------------- ; TriMesh (camera, mesh) ; ----------------------------------------------------------------------------- ; Inline version, uses Simon Armstrong's line function (which Blitz's line ; function is based on), because you can use it on locked buffers, which turns ; out to be quite a lot faster in this fairly demanding loop... Function TriMesh (usecam, mesh, argb = $FFFFFFFF) ; Save some hassle if the mesh can't be seen... If EntityInView (mesh, usecam) ; Lock current buffer... LockBuffer ; Parse each surface in mesh... For s = 1 To CountSurfaces (mesh) surf = GetSurface (mesh, s) ; Parse each triangle in surface... For t = 0 To CountTriangles (surf) - 1 ; Get triangle's vertice positions... presumably these are ; in anti-clockwise order (since it appears to work :) v0 = TriangleVertex (surf, t, 0) v1 = TriangleVertex (surf, t, 1) v2 = TriangleVertex (surf, t, 2) ; --------------------------------------------------------- ; Mark's code for backface culling... ; --------------------------------------------------------- ; Vertex positions... x0# = VertexX (surf, v0) y0# = VertexY (surf, v0) z0# = VertexZ (surf, v0) x1# = VertexX (surf, v1) y1# = VertexY (surf, v1) z1# = VertexZ (surf, v1) x2# = VertexX (surf, v2) y2# = VertexY (surf, v2) z2# = VertexZ (surf, v2) ; Deltas... dx1# = x1 - x0: dy1# = y1 - y0: dz1# = z1 - z0 dx2# = x2 - x0: dy2# = y2 - y0: dz2# = z2 - z0 ; Cross product... cx# = dy1 * dz2 - dy2 * dz1 cy# = dz1 * dx2 - dz2 * dx1 cz# = dx1 * dy2 - dx2 * dy1 ; Normalize... sz# = Sqr (cx * cx + cy * cy + cz * cz) cx = cx / sz: cy = cy / sz: cz = cz / sz ; Plane offset... dt# = -(cx * x0 + cy * y0 + cz * z0) ; Transform eye to mesh coords... TFormPoint 0, 0, 0, usecam, mesh ; Super-complicated cull-decision stuff... If TFormedX () * cx + TFormedY () * cy + TFormedZ () * cz + dt > 0 ; ----------------------------------------------------- ; Get 2D position for each point of triangle... ; ----------------------------------------------------- TFormPoint (x0, y0, z0, mesh, 0) CameraProject usecam, TFormedX (), TFormedY (), TFormedZ () vx0 = ProjectedX () vy0 = ProjectedY () TFormPoint (x1, y1, z1, mesh, 0) CameraProject usecam, TFormedX (), TFormedY (), TFormedZ () vx1 = ProjectedX () vy1 = ProjectedY () TFormPoint (x2, y2, z2, mesh, 0) CameraProject usecam, TFormedX (), TFormedY (), TFormedZ () vx2 = ProjectedX () vy2 = ProjectedY () ; ----------------------------------------------------- ; Draw triangle... ; ----------------------------------------------------- AcidLine (vx0, vy0, vx1, vy1, argb) AcidLine (vx1, vy1, vx2, vy2, argb) AcidLine (vx2, vy2, vx0, vy0, argb) EndIf Next Next ; Unlock locked buffer... UnlockBuffer EndIf End Function ; ----------------------------------------------------------------------------- ; Simon Armstrong's Line function, slightly modified: I lock the buffers once ; per TriMesh call, so disabled that here -- be sure to re-enabled the commented ; out Lock/UnlockBuffer lines if you use this elsewhere! ; ----------------------------------------------------------------------------- Function AcidLine (x0, y0, x1, y1, argb) cx0 = 0 cy0 = 0 cx1 = GraphicsWidth () - 1 cy1 = GraphicsHeight () - 1 While True clip0 = 0 clip1 = 0 If y0 > cy1 clip0 = clip0 Or 1 Else If y0 < cy0 clip0 = clip0 Or 2 If x0 > cx1 clip0 = clip0 Or 4 Else If x0 < cx0 clip0 = clip0 Or 8 If y1 > cy1 clip1 = clip1 Or 1 Else If y1 < cy0 clip1 = clip1 Or 2 If x1 > cx1 clip1 = clip1 Or 4 Else If x1 < cx0 clip1 = clip1 Or 8 If (clip0 Or clip1) = 0 Exit ;draw Line If (clip0 And clip1) Return ;outside If (clip0 And 1) = 1 x0 = x0 + ((x1 - x0) * (cy1 - y0)) / (y1 - y0) y0 = cy1 Goto continue If (clip0 And 2) = 2 x0 = x0 + ((x1 - x0) * (cy0 - y0)) / (y1 - y0) y0 = cy0 Goto continue If (clip0 And 4) = 4 y0 = y0 + ((y1 - y0) * (cx1 - x0)) / (x1 - x0) x0 = cx1 Goto continue If (clip0 And 8) = 8 y0 = y0 + ((y1 - y0) * (cx0 - x0)) / (x1 - x0) x0 = cx0 Goto continue If (clip1 And 1) = 1 x1 = x0 + ((x1 - x0) * (cy1 - y0)) / (y1 - y0) y1 = cy1 Goto continue If (clip1 And 2) = 2 x1 = x0 + ((x1 - x0) * (cy0 - y0)) / (y1 - y0) y1 = cy0 Goto continue If (clip1 And 4) = 4 y1 = y0 + ((y1 - y0) * (cx1 - x0)) / (x1 - x0) x1 = cx1 Goto continue If (clip1 And 8) = 8 y1 = y0 + ((y1 - y0) * (cx0 - x0)) / (x1 - x0) x1 = cx0 Goto continue .continue Wend dx = x1 - x0 dy = y1 - y0 ;RuntimeError dx If (dx Or dy) = 0 WritePixel x0, y0, argb Return EndIf If (dx >= 0) sx = 1: ax = dx Else sx =-1: ax = -dx If (dy >= 0) sy = 1: ay = dy Else sy =-1: ay = -dy ; LockBuffer GraphicsBuffer () If (ax > ay) ddf = ay + ay - ax sadj = ax + ax padj = ay + ay While (ax > -1);0) WritePixelFast x0, y0, argb x0 = x0 + sx ddf = ddf + padj If (ddf > 0) y0 = y0 + sy: ddf = ddf - sadj ax = ax - 1 Wend Else ddf = ax + ax - ay sadj = ay + ay padj = ax + ax While (ay > -1);0) WritePixelFast x0, y0, argb y0 = y0 + sy ddf = ddf + padj If (ddf > 0) x0 = x0 + sx: ddf = ddf - sadj ay = ay - 1 Wend EndIf ; UnlockBuffer GraphicsBuffer () End Function ; ----------------------------------------------------------------------------- ; Demo... ; ----------------------------------------------------------------------------- AppTitle "TriMesh: Use cursors, plus A & Z... SPACE draws lines" Graphics3D 640, 480, 0, 2 ; Our camera... cam = CreateCamera () CameraClsColor cam, 32, 64, 96 MoveEntity cam, 0, 0, -5 ; A cube, yesterday... cube = CreateCube () EntityColor cube, 128, 128, 64 ; A light... light = CreateLight () PositionEntity light, -100, 20, -50 PointEntity light, cube Repeat TurnEntity cube, 0.1, 0.2, 0.4 If KeyDown (203) TranslateEntity cube, -0.1, 0, 0 If KeyDown (205) TranslateEntity cube, 0.1, 0, 0 If KeyDown (200) TranslateEntity cube, 0, 0.1, 0 If KeyDown (208) TranslateEntity cube, 0, -0.1, 0 If KeyDown (30) TranslateEntity cube, 0, 0, 0.1 If KeyDown (44) TranslateEntity cube, 0, 0, -0.1 RenderWorld If KeyDown (57) TriMesh cam, cube Else EntityAlpha cube, 1 EndIf Flip Until KeyHit (1) End |
Comments
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| I would have called this "wireframe overlay on frontfaces". Thanks, |
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