1 files changed, 36 insertions, 0 deletions
diff --git a/src/shader/CalcGradient_glsl_ps.h b/src/shader/CalcGradient_glsl_ps.h
new file mode 100644
index 0000000..2ef7ed8
--- /dev/null
+++ b/src/shader/CalcGradient_glsl_ps.h
@@ -0,0 +1,36 @@
+R"glsl(
+//------------------------------------------------------------------------------------
+// Global variables
+//------------------------------------------------------------------------------------
+
+uniform vec4 g_Scales;
+uniform vec4 g_OneTexel_Left;
+uniform vec4 g_OneTexel_Right;
+uniform vec4 g_OneTexel_Back;
+uniform vec4 g_OneTexel_Front;
+
+uniform sampler2D g_samplerDisplacementMap;
+
+varying float2 vInterpTexCoord;
+
+void main()
+{
+	// Sample neighbour texels
+	float3 displace_left	= texture(g_samplerDisplacementMap, vInterpTexCoord.xy + g_OneTexel_Left.xy).rgb;
+	float3 displace_right	= texture(g_samplerDisplacementMap, vInterpTexCoord.xy + g_OneTexel_Right.xy).rgb;
+	float3 displace_back	= texture(g_samplerDisplacementMap, vInterpTexCoord.xy + g_OneTexel_Back.xy).rgb;
+	float3 displace_front	= texture(g_samplerDisplacementMap, vInterpTexCoord.xy + g_OneTexel_Front.xy).rgb;
+	
+	// -------- Do not store the actual normal value, instead, it preserves two differential values.
+	float2 gradient = float2(-(displace_right.z - displace_left.z) / max(0.01,1.0 + g_Scales.y*(displace_right.x - displace_left.x)), -(displace_front.z - displace_back.z) / max(0.01,1.0+g_Scales.y*(displace_front.y - displace_back.y)));
+	//float2 gradient = {-(displace_right.z - displace_left.z), -(displace_front.z - displace_back.z) };
+	
+	// Calculate Jacobian corelation from the partial differential of displacement field
+	float2 Dx = (displace_right.xy - displace_left.xy) * g_Scales.x;
+	float2 Dy = (displace_front.xy - displace_back.xy) * g_Scales.x;
+	float J = (1.0f + Dx.x) * (1.0f + Dy.y) - Dx.y * Dy.x;
+
+	// Output
+	gl_FragColor = float4(gradient, J, 0);
+}
+)glsl";