Implement Reverse Z projection matrix for skin model

Signed-off-by: Dylan Schooner <dschooner05@gmail.com>

launcher/resources/shaders/shaders.qrc

@@ -1,6 +1,7 @@
 <RCC>
     <qresource prefix="/shaders">
-        <file>vshader.glsl</file>
+        <file>vshader_skin_model.glsl</file>
+        <file>vshader_skin_background.glsl</file>
         <file>fshader.glsl</file>
     </qresource>
 </RCC>

launcher/resources/shaders/vshader_skin_background.glsl

@@ -0,0 +1,11 @@
+
+attribute vec4 a_position;
+attribute vec2 a_texcoord;
+
+varying vec2 v_texcoord;
+
+void main()
+{
+    gl_Position = a_position;
+    v_texcoord = a_texcoord;
+}

launcher/resources/shaders/vshader_skin_model.glsl

@@ -1,6 +1,12 @@
 // Copyright (C) 2024 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 // https://code.qt.io/cgit/qt/qtbase.git/tree/examples/opengl/cube/vshader.glsl
+
+// Dylan Schooner - 2025
+// Modification: Implemented final Z-NDC re-inversion to compensate 
+// for rigid OpenGL 2.0 context forcing glClearDepth(1.0).
+// This flips the high-precision Reverse Z output to the standard [0, W] range.
+
 #ifdef GL_ES
 // Set default precision to medium
 precision mediump int;
@@ -20,6 +26,11 @@ void main()
     // Calculate vertex position in screen space
     gl_Position = mvp_matrix * model_matrix * a_position;
 
+    // Invert the z component of our Reverse Z matrix back to standard NDC
+    float near_z  = gl_Position.z;
+    float w_c     = gl_Position.w;
+    gl_Position.z = w_c - near_z;
+
     // Pass texture coordinate to fragment shader
     // Value will be automatically interpolated to fragments inside polygon faces
     v_texcoord = a_texcoord;