Differences in renders v4 CPU versus GPU
Posted: Sat Nov 12, 2016 8:19 am
Recently downloaded the latest beta build (v4.008) and testing CPU versus GPU rendering on the same Maxwell Studio .MXS scene file. Very notable differences between the two. Here I show the setup of the scene in Maxwell Studio- one close-up and one full (further back) screen capture of the scene:
The scene consists of a metal object (center) and a glass object (to the left) against a simple backdrop. On the right is an HDRI image of a window. There are 3 other light sources in the scene: On the far left is a sphere set to Spot with a map image of a window (which projects against the back wall); light color is pale yellow set to 40 watts. Just left of center is a simple square plane set to Area light with pale yellow color set to Lux=420 directed toward the metal object. Above the objects is a sphere set to Spot with blue color and power=40 watts directed down toward the metal object. The scene was rendered twice in Maxwell Render- once using CPU and once using GPU. The CPU scene ran to level 18; the GPU scene ran to level 20; no other changes between the two scenes. Here are the results:
Notes on the CPU image (the top image): The overhead blue spot is visible on the floor. Nice refractive light path and shadow extend behind the glass object on left. The plane area light does not seem to reflect in the metal object in the middle. Nice shadow beneath the metal object. Note the shadow blocking part of the right side of the projected window pane on the back wall- this is caused by the plane area light being in the path of the sphere spot projecting the window image (though for all emitter lights I chose options to hide from camera + camera in shadow channel + reflections/refractions, so I am not sure why the shadow of the plane area light is showing up). Note very subdued sunlight on the bottom right of the back wall and the floor in front of the right-side HDRI window.
Notes on the GPU image (the bottom image): The overhead blue spot seems to be missing- not visible on the floor. Refractive light path and defined shadow are missing behind the glass object. The plane area light is reflecting in the metal object. Minimal shadow beneath the metal object. No shadow blocking part of the right side of the projected window pane on the back wall (somehow the GPU render ignores the plane light being in the path of the sphere spot). Note much harsher/more powerful sunlight on bottom right of back wall and the floor in front of the right-side HDRI window.
I'm interested in feedback on this test. Which of the differences is being caused by features not yet active in GPU rendering in v4? If not that, what might be causing these differences?
The scene consists of a metal object (center) and a glass object (to the left) against a simple backdrop. On the right is an HDRI image of a window. There are 3 other light sources in the scene: On the far left is a sphere set to Spot with a map image of a window (which projects against the back wall); light color is pale yellow set to 40 watts. Just left of center is a simple square plane set to Area light with pale yellow color set to Lux=420 directed toward the metal object. Above the objects is a sphere set to Spot with blue color and power=40 watts directed down toward the metal object. The scene was rendered twice in Maxwell Render- once using CPU and once using GPU. The CPU scene ran to level 18; the GPU scene ran to level 20; no other changes between the two scenes. Here are the results:
Notes on the CPU image (the top image): The overhead blue spot is visible on the floor. Nice refractive light path and shadow extend behind the glass object on left. The plane area light does not seem to reflect in the metal object in the middle. Nice shadow beneath the metal object. Note the shadow blocking part of the right side of the projected window pane on the back wall- this is caused by the plane area light being in the path of the sphere spot projecting the window image (though for all emitter lights I chose options to hide from camera + camera in shadow channel + reflections/refractions, so I am not sure why the shadow of the plane area light is showing up). Note very subdued sunlight on the bottom right of the back wall and the floor in front of the right-side HDRI window.
Notes on the GPU image (the bottom image): The overhead blue spot seems to be missing- not visible on the floor. Refractive light path and defined shadow are missing behind the glass object. The plane area light is reflecting in the metal object. Minimal shadow beneath the metal object. No shadow blocking part of the right side of the projected window pane on the back wall (somehow the GPU render ignores the plane light being in the path of the sphere spot). Note much harsher/more powerful sunlight on bottom right of back wall and the floor in front of the right-side HDRI window.
I'm interested in feedback on this test. Which of the differences is being caused by features not yet active in GPU rendering in v4? If not that, what might be causing these differences?