5 files changed, 145 insertions, 0 deletions
diff --git a/source/lessons/framebuffers/shaders/blend_test.fs.glsl b/source/lessons/framebuffers/shaders/blend_test.fs.glsl
new file mode 100644
index 0000000..23daa14
--- /dev/null
+++ b/source/lessons/framebuffers/shaders/blend_test.fs.glsl
@@ -0,0 +1,14 @@
+#version 330 core
+
+
+in vec2 TexCoords;
+in vec3 VertexWorldPos;
+uniform sampler2D TexId;
+uniform vec4 hlt_color;
+out vec4 FragColor;
+
+void main() {
+    vec4 tex = texture(TexId, TexCoords);
+
+    FragColor = tex;
+}
diff --git a/source/lessons/framebuffers/shaders/depth_test.fs.glsl b/source/lessons/framebuffers/shaders/depth_test.fs.glsl
new file mode 100644
index 0000000..796d849
--- /dev/null
+++ b/source/lessons/framebuffers/shaders/depth_test.fs.glsl
@@ -0,0 +1,30 @@
+#version 330 core
+
+
+in vec2 TexCoords;
+in vec3 VertexWorldPos;
+uniform sampler2D TexId;
+out vec4 FragColor;
+
+uniform float near = 0.1f;
+uniform float far = 100.0f;
+
+/* @note
+float linear_fragment_depth = MakeDepthLinear(non_linear_fragment_depth);
+float scaled_lfd = linear_fragment_depth/far;
+
+gives us the z value in eye space.
+This is purely for learning purposes.
+The equation used in MakeDepthLinear is derived from the PerspectiveProjectionMatrix.
+Take a look at the equation for that in the codebase 
+or here: https://www.songho.ca/opengl/gl_projectionmatrix.html
+*/
+float MakeDepthLinear(float depth) {
+  float ndc = 2.0f*depth - 1;
+  float linear_depth = (2.0 * far * near)/(far + near - ndc*(far - near));
+  return linear_depth;
+}
+
+void main() {
+    FragColor = texture(TexId, TexCoords);
+}
diff --git a/source/lessons/framebuffers/shaders/depth_test.vs.glsl b/source/lessons/framebuffers/shaders/depth_test.vs.glsl
new file mode 100644
index 0000000..b3b81cc
--- /dev/null
+++ b/source/lessons/framebuffers/shaders/depth_test.vs.glsl
@@ -0,0 +1,19 @@
+#version 330 core
+layout(location=0) in vec3 aPos;
+layout(location=1) in vec2 aTex;
+
+uniform mat4 Model;
+uniform mat4 View;
+uniform mat4 Projection;
+
+out vec2 TexCoords;
+out vec3 VertexWorldPos;
+
+// @note: I still do not fully understand how the FragNormal calculation works. Need to make sure I intuitively 
+// get that
+
+void main() {
+  gl_Position = Projection*View*Model*vec4(aPos, 1.0);
+  VertexWorldPos = vec3(Model * vec4(aPos, 1.0));
+  TexCoords = aTex;
+};
diff --git a/source/lessons/framebuffers/shaders/fbo.fs.glsl b/source/lessons/framebuffers/shaders/fbo.fs.glsl
new file mode 100644
index 0000000..afb9e08
--- /dev/null
+++ b/source/lessons/framebuffers/shaders/fbo.fs.glsl
@@ -0,0 +1,72 @@
+#version 330 core
+
+in vec2 TexCoords;
+uniform sampler2D TexId;
+out vec4 FragColor;
+
+vec4 filter_color_invert(vec4 color)
+{
+  vec4 res = vec4(vec3(1.0) - vec3(color), 1.0);
+  return res;
+}
+
+vec4 filter_color_grayscale(vec4 color)
+{
+  // we will need to average the colors
+  // float average = (color.x + color.y + color.z) / 3.0f;
+  // in reality, human our most sensitive towards green and least to blue, so will need to weight those
+  float average = 0.2126 * color.r + 0.7152 * color.g + 0.0722 * color.b;
+  vec4 res = vec4(vec3(average), 1.0);
+
+  return res;
+}
+
+// @note: different kernels for experimentation
+const float kernel_sharpen[9] = float[](
+    -1, -1, -1,
+    -1,  9, -1,
+    -1, -1, -1
+);
+
+const float kernel_blur[9] = float[](
+    1.0/16.0, 2.0/16.0, 1.0/16.0,
+    2.0/16.0, 4.0/16.0, 2.0/16.0,
+    1.0/16.0, 2.0/16.0, 1.0/16.0
+);
+
+const float kernel_edge_detection[9] = float[](
+    1,  1,  1,
+    1, -8,  1,
+    1,  1,  1
+);
+
+vec4 filter_kernal_effects() 
+{
+  const float offset = 1.0/300.0;
+  vec2 offsets[9] = vec2[](
+    vec2(-offset,  offset),    // top left
+    vec2(      0,  offset),    // top center
+    vec2( offset,  offset),    // top right
+    vec2(-offset,       0),    // center left
+    vec2(      0,       0),    // center center
+    vec2( offset,       0),    // center right
+    vec2(-offset, -offset),    // bot left
+    vec2(      0, -offset),    // bot center
+    vec2( offset, -offset)    // bot right
+  );
+
+  float kernal[9] = kernel_edge_detection;
+  vec3 kernalValue = vec3(0.0);
+  vec3 sampleTex[9];
+  for (int i=0; i<9; i++) {
+    sampleTex[i] = vec3(texture(TexId, TexCoords + offsets[i]));
+    kernalValue += (kernal[i] * sampleTex[i]);
+  }
+
+  vec4 res = vec4(kernalValue, 1.0);
+  return res;
+}
+
+void main() {
+    FragColor = filter_kernal_effects();
+}
diff --git a/source/lessons/framebuffers/shaders/fbo.vs.glsl b/source/lessons/framebuffers/shaders/fbo.vs.glsl
new file mode 100644
index 0000000..82d7211
--- /dev/null
+++ b/source/lessons/framebuffers/shaders/fbo.vs.glsl
@@ -0,0 +1,10 @@
+#version 330 core
+layout(location=0) in vec3 aPos;
+layout(location=1) in vec2 aTex;
+
+out vec2 TexCoords;
+
+void main() {
+  gl_Position = vec4(aPos.x, aPos.y, 0.0f, 1.0f);
+  TexCoords = aTex;
+};