Early work on batching stereo better

libraries/gpu/src/gpu/GLBackend.cpp

@@ -248,7 +248,10 @@ void GLBackend::render(Batch& batch) {
     if (!batch.isStereoEnabled()) {
         _stereo._enable = false;
     }
+    _stereo._enable =batch.isStereoEnabled();
 
+    glEnable(GL_CLIP_DISTANCE0);
+    
     {
         PROFILE_RANGE("Transfer");
         renderPassTransfer(batch);
@@ -259,13 +262,15 @@ void GLBackend::render(Batch& batch) {
         renderPassDraw(batch);
     }
 
-    if (_stereo._enable) {
+  /*  if (_stereo._enable) {
         PROFILE_RANGE("RightRender");
         _stereo._pass = 1;
         renderPassDraw(batch);
         _stereo._pass = 0;
-    }
+    }*/
 
+    glDisable(GL_CLIP_DISTANCE0);
+    
     // Restore the saved stereo state for the next batch
     _stereo._enable = savedStereo;
 }
@@ -326,7 +331,12 @@ void GLBackend::do_draw(Batch& batch, size_t paramOffset) {
     GLenum mode = _primitiveToGLmode[primitiveType];
     uint32 numVertices = batch._params[paramOffset + 1]._uint;
     uint32 startVertex = batch._params[paramOffset + 0]._uint;
-    glDrawArrays(mode, startVertex, numVertices);
+    if (isStereo()) {
+        glDrawArraysInstanced(mode, startVertex, numVertices, 2);
+    } else {
+        glDrawArrays(mode, startVertex, numVertices);
+    }
+        
     (void) CHECK_GL_ERROR();
 }
 
@@ -341,7 +351,11 @@ void GLBackend::do_drawIndexed(Batch& batch, size_t paramOffset) {
     auto typeByteSize = TYPE_SIZE[_input._indexBufferType];
     GLvoid* indexBufferByteOffset = reinterpret_cast<GLvoid*>(startIndex * typeByteSize + _input._indexBufferOffset);
 
-    glDrawElements(mode, numIndices, glType, indexBufferByteOffset);
+    if (isStereo()) {
+        glDrawElementsInstanced(mode, numIndices, glType, indexBufferByteOffset, 2);
+    } else {
+        glDrawElements(mode, numIndices, glType, indexBufferByteOffset);
+    }
     (void) CHECK_GL_ERROR();
 }
 
@@ -352,7 +366,7 @@ void GLBackend::do_drawInstanced(Batch& batch, size_t paramOffset) {
     uint32 numVertices = batch._params[paramOffset + 2]._uint;
     uint32 startVertex = batch._params[paramOffset + 1]._uint;
 
-    glDrawArraysInstancedARB(mode, startVertex, numVertices, numInstances);
+    glDrawArraysInstancedARB(mode, startVertex, numVertices, (isStereo() ? 2 * numInstances : numInstances));
     (void) CHECK_GL_ERROR();
 }
 
@@ -370,9 +384,9 @@ void GLBackend::do_drawIndexedInstanced(Batch& batch, size_t paramOffset) {
     GLvoid* indexBufferByteOffset = reinterpret_cast<GLvoid*>(startIndex * typeByteSize + _input._indexBufferOffset);
     
 #if (GPU_INPUT_PROFILE == GPU_CORE_43)
-    glDrawElementsInstancedBaseVertexBaseInstance(mode, numIndices, glType, indexBufferByteOffset, numInstances, 0, startInstance);
+    glDrawElementsInstancedBaseVertexBaseInstance(mode, numIndices, glType, indexBufferByteOffset, (isStereo() ? 2 * numInstances : numInstances), 0, startInstance);
 #else
-    glDrawElementsInstanced(mode, numIndices, glType, indexBufferByteOffset, numInstances);
+    glDrawElementsInstanced(mode, numIndices, glType, indexBufferByteOffset, (isStereo() ? 2 * numInstances : numInstances));
     Q_UNUSED(startInstance); 
 #endif
     (void)CHECK_GL_ERROR();

libraries/gpu/src/gpu/GLBackendTransform.cpp

@@ -32,6 +32,7 @@ void GLBackend::do_setViewportTransform(Batch& batch, size_t paramOffset) {
     memcpy(&_transform._viewport, batch.editData(batch._params[paramOffset]._uint), sizeof(Vec4i));
 
     ivec4& vp = _transform._viewport;
+    glViewport(vp.x, vp.y, vp.z, vp.w);
 
     // Where we assign the GL viewport
     if (_stereo._enable) {
@@ -41,7 +42,7 @@ void GLBackend::do_setViewportTransform(Batch& batch, size_t paramOffset) {
         }
     } 
 
-    glViewport(vp.x, vp.y, vp.z, vp.w);
+//    glViewport(vp.x, vp.y, vp.z, vp.w);
 
     // The Viewport is tagged invalid because the CameraTransformUBO is not up to date and will need update on next drawcall
     _transform._invalidViewport = true;
@@ -213,7 +214,7 @@ void GLBackend::updateTransform(const Batch& batch) {
         glBindBuffer(GL_ARRAY_BUFFER, _transform._drawCallInfoBuffer);
         glVertexAttribIPointer(gpu::Stream::DRAW_CALL_INFO, 2, GL_UNSIGNED_SHORT, 0,
                                _transform._drawCallInfoOffsets[batch._currentNamedCall]);
-        glVertexAttribDivisor(gpu::Stream::DRAW_CALL_INFO, 1);
+        glVertexAttribDivisor(gpu::Stream::DRAW_CALL_INFO, (isStereo() ? 2: 1));
     }
     
     (void)CHECK_GL_ERROR();

libraries/gpu/src/gpu/Transform.slh

@@ -76,6 +76,18 @@ TransformObject getTransformObject() {
      <$viewport$> = <$cameraTransform$>._viewport;
 <@endfunc@>
 
+<@func transformStereoClipsSpace(cameraTransform, clipPos)@>
+    {
+        vec4 eyeClipEdge[2]= vec4[2](vec4(-1,0,0,1), vec4(1,0,0,1));
+        vec2 eyeOffsetScale = vec2(-0.5, +0.5);
+        uint eyeIndex = gl_InstanceID % 2;
+        gl_ClipDistance[0] = dot(<$clipPos$>, eyeClipEdge[eyeIndex]);
+        float newClipPosX = <$clipPos$>.x * 0.5 + eyeOffsetScale[eyeIndex] * <$clipPos$>.w;
+        <$clipPos$>.x = newClipPosX;
+    }
+<@endfunc@>
+
+
 <@func transformModelToEyeWorldAlignedPos(cameraTransform, objectTransform, modelPos, eyeWorldAlignedPos)@>
     <!// Bring the model pos in the world aligned space centered on the eye axis !>
     { // _transformModelToEyeWorldAlignedPos
@@ -92,6 +104,8 @@ TransformObject getTransformObject() {
         <$transformModelToEyeWorldAlignedPos($cameraTransform$, $objectTransform$, $modelPos$, eyeWAPos)$>
 
         <$clipPos$> = <$cameraTransform$>._projectionViewUntranslated * eyeWAPos;
+        
+        <$transformStereoClipsSpace($cameraTransform$, $clipPos$)$>
     }
 <@endfunc@>
 
@@ -101,6 +115,8 @@ TransformObject getTransformObject() {
         <$transformModelToEyeWorldAlignedPos($cameraTransform$, $objectTransform$, $modelPos$, eyeWAPos)$>
         <$clipPos$> = <$cameraTransform$>._projectionViewUntranslated * eyeWAPos;
         <$eyePos$> = vec4((<$cameraTransform$>._view * vec4(eyeWAPos.xyz, 0.0)).xyz, 1.0);
+        
+        <$transformStereoClipsSpace($cameraTransform$, $clipPos$)$>
     }
 <@endfunc@>