[hdx] Show DomeLights as a skydome

Creating the SkydomeTask to render the domeLight texture as a skydome. This additional task is added to
the _renderTaskIds as the first task in the HdxTaskController so that the AOVs are properly cleared.

Fixes #1385

(Internal change: 2182199)

pxr/imaging/hdx/CMakeLists.txt

@@ -59,6 +59,7 @@ pxr_library(hdx
         selectionTracker
         shadowTask
         simpleLightTask
+        skydomeTask
         task
         taskController
         tokens
@@ -95,6 +96,7 @@ pxr_library(hdx
         shaders/renderPassOitVolumeShader.glslfx
         shaders/renderPassShadowShader.glslfx
         shaders/selection.glslfx
+        shaders/skydome.glslfx
         shaders/visualize.glslfx
         textures/StinsonBeach.exr
 

pxr/imaging/hdx/fullscreenShader.cpp

@@ -576,7 +576,21 @@ HdxFullscreenShader::Draw(
     const GfVec4i vp(0, 0, dimensions[0], dimensions[1]);
 
     const bool depthWrite(depthDst);
-    _Draw(_textures, colorDst, depthDst, vp, depthWrite);
+    _Draw(_textures, colorDst, HgiTextureHandle(), depthDst, HgiTextureHandle(), 
+        vp, depthWrite);
+}
+
+void
+HdxFullscreenShader::Draw(
+    HgiTextureHandle const& colorDst,
+    HgiTextureHandle const& colorResolveDst,
+    HgiTextureHandle const& depthDst,
+    HgiTextureHandle const& depthResolveDst,
+    GfVec4i const& viewport)
+{
+    const bool depthWrite(depthDst);
+    _Draw(_textures, colorDst, colorResolveDst, depthDst, depthResolveDst, 
+        viewport, depthWrite);
 }
 
 void
@@ -592,7 +606,9 @@ void
 HdxFullscreenShader::_Draw(
     TextureMap const& textures,
     HgiTextureHandle const& colorDst,
+    HgiTextureHandle const& colorResolveDst,
     HgiTextureHandle const& depthDst,
+    HgiTextureHandle const& depthResolveDst,
     GfVec4i const &viewport,
     bool writeDepth)
 {
@@ -642,27 +658,33 @@ HdxFullscreenShader::_Draw(
         _CreateBufferResources();
     }
 
-    // create a default texture sampler (first time)
+    // Create a default texture sampler (first time)
     _CreateSampler();
 
     // Create or update the resource bindings (textures may have changed)
     _CreateResourceBindings(textures);
 
-    // create pipeline (first time)
+    // Create pipeline (first time)
     _CreatePipeline(colorDst, depthDst, writeDepth);
-    
+
     // Prepare graphics cmds.
     HgiGraphicsCmdsDesc gfxDesc;
 
     if (colorDst) {
         gfxDesc.colorAttachmentDescs.push_back(_attachment0);
         gfxDesc.colorTextures.push_back(colorDst);
     }
+    if (colorResolveDst) {
+        gfxDesc.colorResolveTextures.push_back(colorResolveDst);
+    }
 
     if (depthDst) {
         gfxDesc.depthAttachmentDesc = _depthAttachment;
         gfxDesc.depthTexture = depthDst;
     }
+    if (depthResolveDst) {
+        gfxDesc.depthResolveTexture = depthResolveDst;
+    }
 
     // Begin rendering
     HgiGraphicsCmdsUniquePtr gfxCmds = _hgi->CreateGraphicsCmds(gfxDesc);

pxr/imaging/hdx/fullscreenShader.h

@@ -129,6 +129,13 @@ class HdxFullscreenShader
     void Draw(HgiTextureHandle const& colorDst,
               HgiTextureHandle const& depthDst);
 
+    HDX_API
+    void Draw(HgiTextureHandle const& colorDst,
+              HgiTextureHandle const& colorResolveDst,
+              HgiTextureHandle const& depthDst,
+              HgiTextureHandle const& depthResolveDst,
+              GfVec4i const& viewport);
+
 private:
     HdxFullscreenShader() = delete;
 
@@ -157,11 +164,14 @@ class HdxFullscreenShader
     bool _CreateSampler();
 
     // Internal draw method
-    void _Draw(TextureMap const& textures, 
-               HgiTextureHandle const& colorDst,
-               HgiTextureHandle const& depthDst,
-               GfVec4i const &viewport,
-               bool depthWrite);
+    void _Draw(
+        TextureMap const& textures, 
+        HgiTextureHandle const& colorDst,
+        HgiTextureHandle const& colorResolveDst,
+        HgiTextureHandle const& depthDst,
+        HgiTextureHandle const& depthResolveDst,
+        GfVec4i const &viewport,
+        bool depthWrite);
 
     static HgiShaderFunctionDesc GetFullScreenVertexDesc();
 

pxr/imaging/hdx/package.cpp

@@ -162,6 +162,13 @@ HdxPackageOutlineShader()
     return shader;
 }
 
+TfToken
+HdxPackageSkydomeShader()
+{
+    static TfToken shader = _GetShaderPath("skydome.glslfx");
+    return shader;
+}
+
 TfToken
 HdxPackageDefaultDomeLightTexture()
 {

pxr/imaging/hdx/package.h

@@ -46,6 +46,7 @@ TfToken HdxPackageRenderPassOitOpaqueShader();
 TfToken HdxPackageRenderPassOitVolumeShader();
 TfToken HdxPackageOitResolveImageShader();
 TfToken HdxPackageOutlineShader();
+TfToken HdxPackageSkydomeShader();
 
 TfToken HdxPackageDefaultDomeLightTexture();
 

pxr/imaging/hdx/shaders/skydome.glslfx

@@ -0,0 +1,84 @@
+-- glslfx version 0.1
+
+//
+// Copyright 2021 Pixar
+//
+// Licensed under the Apache License, Version 2.0 (the "Apache License")
+// with the following modification; you may not use this file except in
+// compliance with the Apache License and the following modification to it:
+// Section 6. Trademarks. is deleted and replaced with:
+//
+// 6. Trademarks. This License does not grant permission to use the trade
+//    names, trademarks, service marks, or product names of the Licensor
+//    and its affiliates, except as required to comply with Section 4(c) of
+//    the License and to reproduce the content of the NOTICE file.
+//
+// You may obtain a copy of the Apache License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the Apache License with the above modification is
+// distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the Apache License for the specific
+// language governing permissions and limitations under the Apache License.
+//
+
+-- configuration
+{
+    "techniques": {
+        "default": {
+            "SkydomeFragment": {
+                "source": [ "Skydome.Fragment" ]
+            }
+        }
+    }
+}
+
+-- glsl Skydome.Fragment
+
+const float PI = 3.1415926535898;
+const float farPlane = 1.0;
+
+float wrapSampleValue(float value)
+{
+    if (value < 0.0) {
+        value += 1.0;
+    }
+    else if (value > 1.0) {
+        value -= 1.0;
+    }
+    return value;
+}
+
+// from PreviewSurface.glslfx
+vec2 projectToLatLong(vec3 sample3D)
+{
+    // project spherical coord onto latitude-longitude map with
+    // latitude: +y == pi/2 and longitude: +z == 0, +x == pi/2
+    float x = (atan(sample3D.z, sample3D.x) + 0.5 * PI) / (2.0 * PI);
+    float y = acos(sample3D.y) / PI;
+
+    return vec2(wrapSampleValue(x), wrapSampleValue(y));
+}
+
+
+void main(void)
+{
+    // Transform the UV coordinates into NDC space and place at the far plane
+    // (z = 1) before transforming into view space.
+    vec2 uvOut_ndc = (uvOut * vec2(2.0)) - vec2(1.0);
+    vec4 uvOut_view = invProjMatrix * vec4(uvOut_ndc, farPlane, 1.0);
+
+    // Normalize to use as the initial sampleDirection
+    vec3 sampleDirection = normalize(uvOut_view.xyz);
+
+    // Apply the camera rotation and lightTransform to the sampleDirection
+    sampleDirection = 
+        ( lightTransform * viewToWorld * vec4(sampleDirection, 0.0) ).xyz;
+
+    // Sample Skydome Texture with the sampleDirection
+    vec2 sampleCoord = projectToLatLong(sampleDirection);
+    hd_FragColor = vec4(HdGet_skydomeTexture(sampleCoord).xyz, 0.0);
+    gl_FragDepth = farPlane;
+}