From 0fe56b1674c99aa75c0dd6f45d77cbff80cf218c Mon Sep 17 00:00:00 2001
From: Marco Lizza <marco.lizza@gmail.com>
Date: Wed, 9 Jan 2019 16:20:56 +0100
Subject: Adding basic palette-switching example using uniform arrays.

---
 .../resources/shaders/glsl100/palette-switch.fs    | 29 +++++++++++++++++++++
 .../resources/shaders/glsl120/palette-switch.fs    | 27 +++++++++++++++++++
 .../resources/shaders/glsl330/palette-switch.fs    | 30 ++++++++++++++++++++++
 3 files changed, 86 insertions(+)
 create mode 100644 examples/shaders/resources/shaders/glsl100/palette-switch.fs
 create mode 100644 examples/shaders/resources/shaders/glsl120/palette-switch.fs
 create mode 100644 examples/shaders/resources/shaders/glsl330/palette-switch.fs

(limited to 'examples/shaders/resources')

diff --git a/examples/shaders/resources/shaders/glsl100/palette-switch.fs b/examples/shaders/resources/shaders/glsl100/palette-switch.fs
new file mode 100644
index 00000000..65a7bd29
--- /dev/null
+++ b/examples/shaders/resources/shaders/glsl100/palette-switch.fs
@@ -0,0 +1,29 @@
+#version 100
+
+precision mediump float;
+
+const int colors = 8;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform ivec3 palette[colors];
+
+void main()
+{
+    // Texel color fetching from texture sampler
+    vec4 texelColor = texture(texture0, fragTexCoord) * fragColor;
+
+    // Convert the (normalized) texel color RED component (GB would work, too)
+    // to the palette index by scaling up from [0, 1] to [0, 255].
+    int index = int(texelColor.r * 255.0);
+    ivec3 color = palette[index];
+
+    // Calculate final fragment color. Note that the palette color components
+    // are defined in the range [0, 255] and need to be normalized to [0, 1]
+    // for OpenGL to work.
+    gl_FragColor = vec4(color / 255.0, texelColor.a);
+}
diff --git a/examples/shaders/resources/shaders/glsl120/palette-switch.fs b/examples/shaders/resources/shaders/glsl120/palette-switch.fs
new file mode 100644
index 00000000..b4384502
--- /dev/null
+++ b/examples/shaders/resources/shaders/glsl120/palette-switch.fs
@@ -0,0 +1,27 @@
+#version 120
+
+const int colors = 8;
+
+// Input fragment attributes (from fragment shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform ivec3 palette[colors];
+
+void main()
+{
+    // Texel color fetching from texture sampler
+    vec4 texelColor = texture(texture0, fragTexCoord) * fragColor;
+
+    // Convert the (normalized) texel color RED component (GB would work, too)
+    // to the palette index by scaling up from [0, 1] to [0, 255].
+    int index = int(texelColor.r * 255.0);
+    ivec3 color = palette[index];
+
+    // Calculate final fragment color. Note that the palette color components
+    // are defined in the range [0, 255] and need to be normalized to [0, 1]
+    // for OpenGL to work.
+    gl_FragColor = vec4(color / 255.0, texelColor.a);
+}
diff --git a/examples/shaders/resources/shaders/glsl330/palette-switch.fs b/examples/shaders/resources/shaders/glsl330/palette-switch.fs
new file mode 100644
index 00000000..178c42c5
--- /dev/null
+++ b/examples/shaders/resources/shaders/glsl330/palette-switch.fs
@@ -0,0 +1,30 @@
+#version 330
+
+const int colors = 8;
+
+// Input fragment attributes (from fragment shader)
+in vec2 fragTexCoord;
+in vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform ivec3 palette[colors];
+
+// Output fragment color
+out vec4 finalColor;
+
+void main()
+{
+    // Texel color fetching from texture sampler
+    vec4 texelColor = texture(texture0, fragTexCoord) * fragColor;
+
+    // Convert the (normalized) texel color RED component (GB would work, too)
+    // to the palette index by scaling up from [0, 1] to [0, 255].
+    int index = int(texelColor.r * 255.0);
+    ivec3 color = palette[index];
+
+    // Calculate final fragment color. Note that the palette color components
+    // are defined in the range [0, 255] and need to be normalized to [0, 1]
+    // for OpenGL to work.
+    finalColor = vec4(color / 255.0, texelColor.a);
+}
-- 
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