[PlanarProbe] Provide full size array of available VP matrices to shaders

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/LightingDebug.cs

         IndirectSpecularOcclusionFromSsao,
         IndirectSpecularGtaoFromSsao,
         EnvironmentProxyVolume,
+        EnvironmentSampleCoordinates,
     }
 
     public enum ShadowMapDebugMode

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/LightingDebug.cs.hlsl

 #define DEBUGLIGHTINGMODE_INDIRECT_SPECULAR_OCCLUSION_FROM_SSAO (7)
 #define DEBUGLIGHTINGMODE_INDIRECT_SPECULAR_GTAO_FROM_SSAO (8)
 #define DEBUGLIGHTINGMODE_ENVIRONMENT_PROXY_VOLUME (9)
+#define DEBUGLIGHTINGMODE_ENVIRONMENT_SAMPLE_COORDINATES (10)
 
 
 #endif

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/LightLoop/LightLoop.cs

 
             m_lightList = new LightList();
             m_lightList.Allocate();
+            m_Env2DCaptureVP.Clear();
+            for (int i = 0, c = Mathf.Max(1, hdAsset.renderPipelineSettings.lightLoopSettings.maxPlanarReflectionProbes); i < c; ++i)
+                m_Env2DCaptureVP.Add(Matrix4x4.identity);
 
             s_DirectionalLightDatas = new ComputeBuffer(k_MaxDirectionalLightsOnScreen, System.Runtime.InteropServices.Marshal.SizeOf(typeof(DirectionalLightData)));
             s_LightDatas = new ComputeBuffer(k_MaxPunctualLightsOnScreen + k_MaxAreaLightsOnScreen, System.Runtime.InteropServices.Marshal.SizeOf(typeof(LightData)));
             var envIndex = -1;
             if (probe.planarReflectionProbe != null)
             {
-                envIndex = m_ReflectionPlanarProbeCache.FetchSlice(cmd, probe.texture);
-                envIndex = (envIndex << 1) | (int)EnvCacheType.Texture2D;
+                var fetchIndex = m_ReflectionPlanarProbeCache.FetchSlice(cmd, probe.texture);
+                envIndex = (fetchIndex << 1) | (int)EnvCacheType.Texture2D;
 
                 float nearClipPlane, farClipPlane, aspect, fov;
                 Color backgroundColor;
 
                 // We transform it to object space by translating the capturePosition
                 var vp = gpuProj * gpuView * Matrix4x4.Translate(capturePosition);
-                m_Env2DCaptureVP.Add(vp);
+                m_Env2DCaptureVP[fetchIndex] = vp;
                 sampleDirectionDiscardWS = captureRotation * Vector3.forward;
             }
             else if (probe.reflectionProbe != null)
                 // If any light require it, we need to enabled bake shadow mask feature
                 m_enableBakeShadowMask = false;
 
-                m_Env2DCaptureVP.Clear();
                 m_lightList.Clear();
 
                 Vector3 camPosWS = camera.transform.position;
                 cmd.SetGlobalTexture(HDShaderIDs._CookieCubeTextures, m_CubeCookieTexArray.GetTexCache());
                 cmd.SetGlobalTexture(HDShaderIDs._EnvCubemapTextures, m_ReflectionProbeCache.GetTexCache());
                 cmd.SetGlobalTexture(HDShaderIDs._Env2DTextures, m_ReflectionPlanarProbeCache.GetTexCache());
-                if (m_Env2DCaptureVP.Count > 0)
-                    cmd.SetGlobalMatrixArray(HDShaderIDs._Env2DCaptureVP, m_Env2DCaptureVP);
+                cmd.SetGlobalMatrixArray(HDShaderIDs._Env2DCaptureVP, m_Env2DCaptureVP);
 
                 cmd.SetGlobalBuffer(HDShaderIDs._DirectionalLightDatas, s_DirectionalLightDatas);
                 cmd.SetGlobalInt(HDShaderIDs._DirectionalLightCount, m_lightList.directionalLights.Count);

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/LightLoop/LightLoopDef.hlsl

             float4 color = SAMPLE_TEXTURE2D_ARRAY_LOD(_Env2DTextures, s_trilinear_clamp_sampler, ndc.xy, index, 0);
             color.a = any(ndc.xyz < 0) || any(ndc.xyz > 1) ? 0 : 1;
             
+#ifdef DEBUG_DISPLAY
+            if (_DebugLightingMode == DEBUGLIGHTINGMODE_ENVIRONMENT_SAMPLE_COORDINATES)
+                return float4(ndc.xy, 0, color.a);
+#endif
             return color;
         }
         else if (cacheType == ENVCACHETYPE_CUBEMAP)
+
+#ifdef DEBUG_DISPLAY
+            if (_DebugLightingMode == DEBUGLIGHTINGMODE_ENVIRONMENT_SAMPLE_COORDINATES)
+                return float4(texCoord.xyz * 0.5 + 0.5, color.a);
+#endif
             return color;
         }
         return float4(0, 0, 0, 0);