From 11642fd3a218185187bb356f2f446313694d4be4 Mon Sep 17 00:00:00 2001
From: Yuri Kunde Schlesner <yuriks@yuriks.net>
Date: Thu, 28 Aug 2014 15:21:54 -0300
Subject: Rework OpenGL renderer.

The OpenGL renderer has been revised, with the following changes:
 - Initialization and rendering have been refactored to reduce the number of
   redundant objects used.
 - Framebuffer rotation is now done directly, using texture mapping.
 - Vertex coordinates are now given in pixels, and the projection matrix
   isn't hardcoded anymore.
---
 src/video_core/renderer_opengl/gl_shaders.h | 46 ++++++++++++++++-------------
 1 file changed, 26 insertions(+), 20 deletions(-)

(limited to 'src/video_core/renderer_opengl/gl_shaders.h')

diff --git a/src/video_core/renderer_opengl/gl_shaders.h b/src/video_core/renderer_opengl/gl_shaders.h
index 380648f4..0f88ab80 100644
--- a/src/video_core/renderer_opengl/gl_shaders.h
+++ b/src/video_core/renderer_opengl/gl_shaders.h
@@ -6,34 +6,40 @@
 
 namespace GLShaders {
 
-static const char g_vertex_shader[] = R"(
+const char g_vertex_shader[] = R"(
 #version 150 core
-in vec3 position;
-in vec2 texCoord;
 
-out vec2 UV;
+in vec2 vert_position;
+in vec2 vert_tex_coord;
+out vec2 frag_tex_coord;
 
-mat3 window_scale = mat3(
-                         vec3(1.0, 0.0, 0.0),
-                         vec3(0.0, 5.0/6.0, 0.0), // TODO(princesspeachum): replace hard-coded aspect with uniform
-                         vec3(0.0, 0.0, 1.0)
-                         );
+// This is a truncated 3x3 matrix for 2D transformations:
+// The upper-left 2x2 submatrix performs scaling/rotation/mirroring.
+// The third column performs translation.
+// The third row could be used for projection, which we don't need in 2D. It hence is assumed to
+// implicitly be [0, 0, 1]
+uniform mat3x2 modelview_matrix;
 
 void main() {
-    gl_Position.xyz = window_scale * position;
-    gl_Position.w = 1.0;
-
-    UV = texCoord;
-})";
+    // Multiply input position by the rotscale part of the matrix and then manually translate by
+    // the last column. This is equivalent to using a full 3x3 matrix and expanding the vector
+    // to `vec3(vert_position.xy, 1.0)`
+    gl_Position = vec4(mat2(modelview_matrix) * vert_position + modelview_matrix[2], 0.0, 1.0);
+    frag_tex_coord = vert_tex_coord;
+}
+)";
 
-static const char g_fragment_shader[] = R"(
+const char g_fragment_shader[] = R"(
 #version 150 core
-in vec2 UV;
-out vec3 color;
-uniform sampler2D sampler;
+
+in vec2 frag_tex_coord;
+out vec4 color;
+
+uniform sampler2D color_texture;
 
 void main() {
-    color = texture(sampler, UV).rgb;
-})";
+    color = texture(color_texture, frag_tex_coord);
+}
+)";
 
 }
-- 
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