Example of pulling math out of loop using more increments
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19
main.c
19
main.c
@ -58,22 +58,25 @@ void drawTexInto(struct texture tex, struct texture buffer, struct rect texbound
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i32 stepy = 256 * (float)texheight / outheight;
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i32 texx = 256 * texbounds.x1;
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i32 texy = 256 * texbounds.y1;
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i32 bufy = 3 * (bufbounds.x1 + bufbounds.y1 * buffer.width);
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i32 bufyinc = 3 * buffer.width;
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i32 bufi = bufy;
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//log("%f,%f step %f,%f", texx, texy, stepx, stepy);
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// Buffer is R G B for each pixel, then across then down. If you want X, Y,
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// it's: 3 * (x + y * width)
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for(int y = bufbounds.y1; y < bufbounds.y2; y++) {
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texx = texbounds.x1;
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bufi = bufy;
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for(int x = bufbounds.x1; x < bufbounds.x2; x++) {
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i32 texi = 3 * ((texx >> 8) + tex.width * (texy >> 8));
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i32 bufi = 3 * (x + buffer.width * y);
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// You can get rid of this for loop for more performance, but probably
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// not a big deal with -O3, it'll be unrolled
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buffer.data[bufi] = tex.data[texi];
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buffer.data[bufi + 1] = tex.data[texi + 1];
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buffer.data[bufi + 2] = tex.data[texi + 2];
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memcpy(buffer.data + bufi, tex.data + texi, 3);
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texx += stepx;
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bufi += 3;
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}
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texy += stepy;
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bufy += bufyinc;
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}
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}
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@ -98,10 +101,10 @@ int main() {
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// We actually stretch a texture here
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struct rect texrect = { 0, 0, 16, 16 };
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struct rect bufrect = { 10, 10, 26, 26 };
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struct rect bufrect = { 10, 10, 509, 499 };
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clock_t start = clock();
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for(int i = 0; i < 50000; i++) { //overdraw factor
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for(int i = 0; i < 50; i++) { //overdraw factor
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drawTexInto(tex, fb, texrect, bufrect);
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}
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clock_t end = clock();
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