more documentation. Image base impl

resources/shaders/simple_image.vertex

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+#version 450
+// SIMPLE IMAGE : VERTEX SHADER
+
+// These come in from the vertex definition
+layout(location = 0) in vec2 position;
+
+// These are made up in the shader themselves
+layout(location = 0) out vec2 img_coords;
+
+void main() {
+
+    gl_Position = vec4(position, 0.0, 1.0);
+    img_coords = position;
+}
+
+
+
+