From 9f097e64e216c4e6d61ceddf4518cb475936094b Mon Sep 17 00:00:00 2001
From: bjornbytes <tie.372@gmail.com>
Date: Tue, 13 Jun 2017 20:04:51 -0700
Subject: [PATCH] Add lovrNormalMatrix;

---
 src/graphics/shader.c | 14 ++++++++++++++
 src/math/mat4.c       | 20 ++++++++++++++++++++
 src/math/mat4.h       |  1 +
 3 files changed, 35 insertions(+)

diff --git a/src/graphics/shader.c b/src/graphics/shader.c
index 7663ef1a..982e6824 100644
--- a/src/graphics/shader.c
+++ b/src/graphics/shader.c
@@ -19,6 +19,7 @@ const char* lovrShaderVertexPrefix = ""
 "out vec2 texCoord; \n"
 #endif
 "uniform mat4 lovrTransform; \n"
+"uniform mat3 lovrNormalMatrix; \n"
 "uniform mat4 lovrProjection; \n"
 "";
 
@@ -229,6 +230,19 @@ void lovrShaderBind(Shader* shader, mat4 transform, mat4 projection, unsigned in
     int uniformId = lovrShaderGetUniformId(shader, "lovrTransform");
     lovrShaderSendFloatMat4(shader, uniformId, transform);
     memcpy(shader->transform, transform, 16 * sizeof(float));
+
+    float normalMatrix[16];
+    mat4_set(normalMatrix, transform);
+    normalMatrix[12] = normalMatrix[13] = normalMatrix[14] = 0;
+    normalMatrix[15] = 1;
+    mat4_transpose(mat4_invert(normalMatrix));
+    float normalMatrix3x3[9] = {
+      normalMatrix[0], normalMatrix[1], normalMatrix[2],
+      normalMatrix[4], normalMatrix[5], normalMatrix[6],
+      normalMatrix[8], normalMatrix[9], normalMatrix[10]
+    };
+    uniformId = lovrShaderGetUniformId(shader, "lovrNormalMatrix");
+    lovrShaderSendFloatMat3(shader, uniformId, normalMatrix3x3);
   }
 
   // Update projection if necessary
diff --git a/src/math/mat4.c b/src/math/mat4.c
index 9b63efbd..e1072841 100644
--- a/src/math/mat4.c
+++ b/src/math/mat4.c
@@ -106,6 +106,26 @@ mat4 mat4_invert(mat4 m) {
   return m;
 }
 
+mat4 mat4_transpose(mat4 m) {
+  float a01 = m[1], a02 = m[2], a03 = m[3],
+        a12 = m[6], a13 = m[7],
+        a23 = m[11];
+
+  m[1] = m[4];
+  m[2] = m[8];
+  m[3] = m[12];
+  m[4] = a01;
+  m[6] = m[9];
+  m[7] = m[13];
+  m[8] = a02;
+  m[9] = a12;
+  m[11] = m[14];
+  m[12] = a03;
+  m[13] = a13;
+  m[14] = a23;
+  return m;
+}
+
 // Modified from gl-matrix.c
 mat4 mat4_multiply(mat4 m, mat4 n) {
   float m00 = m[0], m01 = m[1], m02 = m[2], m03 = m[3],
diff --git a/src/math/mat4.h b/src/math/mat4.h
index 42a99318..f9936e5a 100644
--- a/src/math/mat4.h
+++ b/src/math/mat4.h
@@ -8,6 +8,7 @@ mat4 mat4_fromMat34(mat4 m, float (*n)[4]);
 mat4 mat4_fromMat44(mat4 m, float (*n)[4]);
 mat4 mat4_identity(mat4 m);
 mat4 mat4_invert(mat4 m);
+mat4 mat4_transpose(mat4 m);
 mat4 mat4_multiply(mat4 m, mat4 n);
 mat4 mat4_translate(mat4 m, float x, float y, float z);
 mat4 mat4_rotate(mat4 m, float angle, float x, float y, float z);