From 699d0e2e87c227fabcc6022e5324d0ec44d032bc Mon Sep 17 00:00:00 2001
From: Brendan Hansen <brendan.f.hansen@gmail.com>
Date: Sun, 18 Oct 2020 21:42:59 -0500
Subject: [PATCH] added mat4_mul

---
 include/vecmath.h            |  1 +
 res/shaders/planet_vert.glsl |  2 +-
 src/sim.c                    | 25 ++++++++++++++-----------
 src/vecmath.c                | 15 +++++++++++++++
 4 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/include/vecmath.h b/include/vecmath.h
index be7d436..0916674 100644
--- a/include/vecmath.h
+++ b/include/vecmath.h
@@ -22,6 +22,7 @@ void mat4_ortho(mat4 *mat,
                 f32 top, f32 bottom,
                 f32 near, f32 far);
 void mat4_proj(mat4 *mat);
+void mat4_mul(mat4 a, mat4 b, mat4* out);
 
 
 #endif //VECMATH_H
diff --git a/res/shaders/planet_vert.glsl b/res/shaders/planet_vert.glsl
index 67afc25..4c306ce 100644
--- a/res/shaders/planet_vert.glsl
+++ b/res/shaders/planet_vert.glsl
@@ -9,5 +9,5 @@ layout(location = 2) in float a_mass;
 uniform mat4 u_proj;
 
 void main() {
-	gl_Position = u_proj * vec4(a_shape_pos, 0, 1);
+	gl_Position = u_proj * vec4(a_shape_pos * a_mass + a_obj_pos, 0, 1);
 }
\ No newline at end of file
diff --git a/src/sim.c b/src/sim.c
index c017067..d091e1f 100644
--- a/src/sim.c
+++ b/src/sim.c
@@ -56,9 +56,16 @@ init_glfw() {
 	glfwSetKeyCallback(window, glfw_key_handler);
 	glfwSetFramebufferSizeCallback(window, glfw_resize_handler);
     
-    //glEnable(GL_CULL_FACE);
-    //glFrontFace(GL_CW);
-    //glCullFace(GL_BACK);
+    // NOTE(Brendan): This may need to be changed if the screen orientation changes.
+    glEnable(GL_CULL_FACE);
+    glFrontFace(GL_CW);
+    glCullFace(GL_BACK);
+}
+
+internal void
+deinit_glfw() {
+	glfwDestroyWindow(window);
+	glfwTerminate();
 }
 
 internal GLuint
@@ -144,8 +151,8 @@ create_circle_mesh() {
     V2f circle_points[CIRCLE_POINT_COUNT] = {};
     foreach (i, 0, CIRCLE_POINT_COUNT) {
         f32 t = (f32) i / (f32) CIRCLE_POINT_COUNT;
-        circle_points[i].x = cos(t * 2 * PI) * 100.0f + 400.0f;
-        circle_points[i].y = sin(t * 2 * PI) * 100.0f + 200.0f;
+        circle_points[i].x = cos(t * 2 * PI) / 2.0f + 400.0f;
+        circle_points[i].y = sin(t * 2 * PI) / 2.0f + 200.0f;
     }
     
     GLsizei vertex_buffer;
@@ -169,11 +176,7 @@ create_circle_mesh() {
     return vao;
 }
 
-internal void
-deinit_opengl() {
-	glfwDestroyWindow(window);
-	glfwTerminate();
-}
+
 
 // NOTE(Brendan): dt is expected to be in units of "per second".
 internal void
@@ -231,7 +234,7 @@ main(i32 argc, char* argv[]) {
     
     loop();
     
-    deinit_opengl();
+    deinit_glfw();
     
     return 0;
 }
\ No newline at end of file
diff --git a/src/vecmath.c b/src/vecmath.c
index 01b4a38..25af422 100644
--- a/src/vecmath.c
+++ b/src/vecmath.c
@@ -74,3 +74,18 @@ mat4_ortho(mat4 *mat,
     (*mat)[3 * 4 + 1] = -(top + bottom) / (top - bottom);
     (*mat)[3 * 4 + 2] = -(far + near) / (far - near);
 }
+
+
+void
+mat4_mul(mat4 a, mat4 b, mat4* out)
+{
+    foreach(row, 0, 4) {
+        foreach(col, 0, 4) {
+            (*out)[row * 4 + col] = 0.0f;
+            
+            foreach(i, 0, 4) {
+                (*out)[row * 4 + col] += a[row * 4 + i] + b[i * 4 + col];
+            }
+        }
+    }
+}
\ No newline at end of file
-- 
2.25.1