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// worldocull.cpp: occlusion map and occlusion test
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void toggleocull() { ocull = !ocull; }
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COMMAND(toggleocull, ARG_NONE);
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// constructs occlusion map: cast rays in all directions on the 2d plane and record distance.
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// done exactly once per frame.
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void disableraytable()
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loopi(NUMRAYS) rdist[i] = 1e16f;
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void computeraytable(float vx, float vy, float fov)
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if(!ocull) { disableraytable(); return; }
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odist = getvar("fog")*1.5f;
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float apitch = (float)fabs(camera1->pitch);
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float af = fov/2+apitch/1.5f+3;
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float byaw = (camera1->yaw-90+af)/360*PI2;
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float syaw = (camera1->yaw-90-af)/360*PI2;
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float angle = i*PI2/NUMRAYS;
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if((apitch>45 // must be bigger if fov>120
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|| (angle<byaw && angle>syaw)
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|| (angle<byaw-PI2 && angle>syaw-PI2)
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|| (angle<byaw+PI2 && angle>syaw+PI2))
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&& !SOLID(S(int(vx), int(vy)))) // try to avoid tracing ray if outside of frustrum
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float ray = i*8/(float)NUMRAYS;
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if(ray>1 && ray<3) { dx = -(ray-2); dy = 1; }
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else if(ray>=3 && ray<5) { dx = -1; dy = -(ray-4); }
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else if(ray>=5 && ray<7) { dx = ray-6; dy = -1; }
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else { dx = 1; dy = ray>4 ? ray-8 : ray; }
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if(SOLID(S(int(sx), int(sy)))) // 90% of time spend in this function is on this line
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rdist[i] = (float)(fabs(sx-vx)+fabs(sy-vy));
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// test occlusion for a cube... one of the most computationally expensive functions in the engine
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// as its done for every cube and entity, but its effect is more than worth it!
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// GCC seems to have trouble inlining these
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#define ca(xv, yv) ({ float x = (xv), y = (yv); x>y ? y/x : 2-x/y; })
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#define ma(xv, yv) ({ float x = (xv), y = (yv); x==0 ? (y>0 ? 2 : -2) : y/x; })
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static inline float ca(float x, float y) { return x>y ? y/x : 2-x/y; }
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static inline float ma(float x, float y) { return x==0 ? (y>0 ? 2 : -2) : y/x; }
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int isoccluded(float vx, float vy, float cx, float cy, float csize) // v = viewer, c = cube to test
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// - check middle cube? BG
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// find highest and lowest angle in the occlusion map that this cube spans, based on its most left and right
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// points on the border from the viewer pov... I see no easier way to do this than this silly code below
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float xdist = 0, ydist = 0, h, l;
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if(cx+csize<vx) // ADF
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if((xdist = vx-(cx+csize)) > odist) return 2;
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if(cy+csize<vy) { if((ydist = vy-(cy+csize)) > odist) return 2; h = ca(-(cx-vx), ydist)+4; l = ca(xdist, -(cy-vy))+4; } // A
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else { h = ma(xdist, -(cy+csize-vy))+4; l = ma(xdist, -(cy-vy))+4; } // D
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else { if((ydist = cy-vy) > odist) return 2; h = ca(cy+csize-vy, xdist)+2; l = ca(ydist, -(cx-vx))+2; } // F
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if(cy+csize<vy) { if((ydist = vy-(cy+csize)) > odist) return 2; h = ma(ydist, cx-vx)+6; l = ma(ydist, cx+csize-vx)+6; } // B
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else { if((ydist = cy-vy) > odist) return 2; h = ma(ydist, -(cx+csize-vx))+2; l = ma(ydist, -(cx-vx))+2; } // G
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if((xdist = cx-vx) > odist) return 2;
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if(cy+csize<vy) { if((ydist = vy-(cy+csize)) > odist) return 2; h = ca(-(cy-vy), xdist)+6; l = ca(ydist, cx+csize-vx)+6; } // C
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else { h = ma(xdist, cy-vy); l = ma(xdist, cy+csize-vy); } // E
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else { if((ydist = cy-vy) > odist) return 2; h = ca(cx+csize-vx, ydist); l = ca(xdist, cy+csize-vy); } // H
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float dist = xdist+ydist-1; // 1 needed?
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int si = int(h*(NUMRAYS/8))+NUMRAYS; // get indexes into occlusion map from angles
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int ei = int(l*(NUMRAYS/8))+NUMRAYS+1;
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if(ei<=si) ei += NUMRAYS;
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for(int i = si; i<=ei; i++)
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if(dist<rdist[i&(NUMRAYS-1)]) return 0; // if any value in this segment of the occlusion map is further away then cube is not occluded
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return 1; // cube is entirely occluded
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source/src/worldocull.cpp
