Fix several texture/shader exercises to use updated code viewer.

src/1.getting_started/3.4.shaders_exercise1/shaders_exercise1.cpp

@@ -0,0 +1,11 @@
+#version 330 core
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec3 aColor;
+
+out vec3 ourColor;
+
+void main()
+{
+    gl_Position = vec4(aPos.x, -aPos.y, aPos.z, 1.0); // just add a - to the y position
+    ourColor = aColor;
+}

src/1.getting_started/3.5.shaders_exercise2/shaders_exercise2.cpp

@@ -0,0 +1,20 @@
+// In your CPP file:
+// ======================
+float offset = 0.5f;
+ourShader.setFloat("xOffset", offset);
+
+// In your vertex shader:
+// ======================
+#version 330 core
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec3 aColor;
+
+out vec3 ourColor;
+
+uniform float xOffset;
+
+void main()
+{
+    gl_Position = vec4(aPos.x + xOffset, aPos.y, aPos.z, 1.0); // add the xOffset to the x position of the vertex position
+    ourColor = aColor;
+}

src/1.getting_started/3.6.shaders_exercise3/shaders_exercise3.cpp

@@ -0,0 +1,37 @@
+// Vertex shader:
+// ==============
+#version 330 core
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec3 aColor;
+
+// out vec3 ourColor;
+out vec3 ourPosition;
+
+void main()
+{
+    gl_Position = vec4(aPos, 1.0); 
+    // ourColor = aColor;
+    ourPosition = aPos;
+}
+
+// Fragment shader:
+// ================
+#version 330 core
+out vec4 FragColor;
+// in vec3 ourColor;
+in vec3 ourPosition;
+
+void main()
+{
+    FragColor = vec4(ourPosition, 1.0);    // note how the position value is linearly interpolated to get all the different colors
+}
+
+/* 
+Answer to the question: Do you know why the bottom-left side is black?
+-- --------------------------------------------------------------------
+Think about this for a second: the output of our fragment's color is equal to the (interpolated) coordinate of 
+the triangle. What is the coordinate of the bottom-left point of our triangle? This is (-0.5f, -0.5f, 0.0f). Since the
+xy values are negative they are clamped to a value of 0.0f. This happens all the way to the center sides of the 
+triangle since from that point on the values will be interpolated positively again. Values of 0.0f are of course black
+and that explains the black side of the triangle.
+*/

src/1.getting_started/4.3.textures_exercise1/textures_exercise1.cpp

@@ -0,0 +1,13 @@
+#version 330 core
+out vec4 FragColor;
+
+in vec3 ourColor;
+in vec2 TexCoord;
+
+uniform sampler2D ourTexture1;
+uniform sampler2D ourTexture2;
+
+void main()
+{
+    FragColor = mix(texture(ourTexture1, TexCoord), texture(ourTexture2, vec2(1.0 - TexCoord.x, TexCoord.y)), 0.2);
+}