86 lines
1.6 KiB
C
86 lines
1.6 KiB
C
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#pragma once
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typedef struct vec3 {
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float v[3];
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} vec3;
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typedef struct vec4 {
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float v[4];
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} vec4;
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typedef struct mat3 {
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float v[3*3];
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} mat3;
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typedef struct mat4 {
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float v[4*4];
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} mat4;
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static inline mat3 matmul3(const mat3 &a, const mat3 &b) {
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mat3 ret = {{0.0}};
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for (int r=0; r<3; r++) {
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for (int c=0; c<3; c++) {
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float v = 0.0;
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for (int k=0; k<3; k++) {
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v += a.v[r*3+k] * b.v[k*3+c];
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}
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ret.v[r*3+c] = v;
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}
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}
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return ret;
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}
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static inline vec3 matvecmul3(const mat3 &a, const vec3 &b) {
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vec3 ret = {{0.0}};
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for (int r=0; r<3; r++) {
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for (int c=0; c<3; c++) {
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ret.v[r] += a.v[r*3+c] * b.v[c];
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}
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}
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return ret;
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}
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static inline mat4 matmul(const mat4 &a, const mat4 &b) {
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mat4 ret = {{0.0}};
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for (int r=0; r<4; r++) {
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for (int c=0; c<4; c++) {
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float v = 0.0;
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for (int k=0; k<4; k++) {
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v += a.v[r*4+k] * b.v[k*4+c];
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}
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ret.v[r*4+c] = v;
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}
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}
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return ret;
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}
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static inline vec4 matvecmul(const mat4 &a, const vec4 &b) {
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vec4 ret = {{0.0}};
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for (int r=0; r<4; r++) {
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for (int c=0; c<4; c++) {
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ret.v[r] += a.v[r*4+c] * b.v[c];
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}
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}
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return ret;
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}
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// scales the input and output space of a transformation matrix
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// that assumes pixel-center origin.
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static inline mat3 transform_scale_buffer(const mat3 &in, float s) {
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// in_pt = ( transform(out_pt/s + 0.5) - 0.5) * s
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mat3 transform_out = {{
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1.0f/s, 0.0f, 0.5f,
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0.0f, 1.0f/s, 0.5f,
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0.0f, 0.0f, 1.0f,
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}};
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mat3 transform_in = {{
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s, 0.0f, -0.5f*s,
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0.0f, s, -0.5f*s,
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0.0f, 0.0f, 1.0f,
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}};
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return matmul3(transform_in, matmul3(in, transform_out));
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}
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