Implement Reverse Z projection matrix for skin model

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

launcher/resources/shaders/vshader_skin_model.glsl

@@ -0,0 +1,37 @@
+// 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;
+precision mediump float;
+#endif
+
+uniform mat4 mvp_matrix;
+uniform mat4 model_matrix;
+
+attribute vec4 a_position;
+attribute vec2 a_texcoord;
+
+varying vec2 v_texcoord;
+
+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;
+}