a

1 files changed, 26 insertions, 0 deletions

diff --git a/src/util/math.cpp b/src/util/math.cpp
new file mode 100644
index 0000000..4ab3f2b
--- /dev/null
+++ b/src/util/math.cpp
@@ -0,0 +1,26 @@
+#include "math.h"
+
+#include "../render/gl_3d.h"
+
+VEC2 m_screen_transform( const VEC3 &world ) {
+  GL_DATA* gl          = gl_instance();
+  MAT4* gl_proj_matrix = gl->proj_matrix;
+  VEC2 screen          = gl->viewport_start;
+  VEC3 clip;
+
+  clip.x = world.x * gl_proj_matrix->m[0][0] + world.y * gl_proj_matrix->m[1][0] + world.z * gl_proj_matrix->m[2][0] + gl_proj_matrix->m[3][0];
+  clip.y = world.x * gl_proj_matrix->m[0][1] + world.y * gl_proj_matrix->m[1][1] + world.z * gl_proj_matrix->m[2][1] + gl_proj_matrix->m[3][1];
+  clip.z = world.x * gl_proj_matrix->m[0][3] + world.y * gl_proj_matrix->m[1][3] + world.z * gl_proj_matrix->m[2][3] + gl_proj_matrix->m[3][3];
+
+  if( clip.z <= 0.f ) {
+    screen.x = screen.y = SCREEN_INVALID_POS;
+  }
+
+  F32 ndcx = clip.x / clip.z;
+  F32 ndcy = clip.y / clip.z;
+
+  screen.x += ( ndcx * .5f + .5f ) * (F32)gl->viewport_dim.x;
+  screen.y += ( 1.f - ( ndcy * .5f + .5f ) ) * (F32)gl->viewport_dim.y;
+
+  return screen;
+}