On a recent project, I had to render several cameras. I optimised my settings to achieve a rendering time of approximately 10 seconds per image. One of the cameras moves very close to an object, and when it is closest, the rendering time increases from around ten seconds to 1 minute 30 seconds.
The shader applied to this object is procedural, and the object in question has 2,000 vertices.
Two questions:
Why does the rendering time increase depending on the distance between the camera and the object?
When rendering with multiple cameras, is it possible to ask one of the cameras to stop rendering at a given time?
I could send the project if necessary.
you can find attached the image illustrating my request.
If you remove the material, does the image render faster? Some procedural materials can be heavy, so I would verify if it’s the culprit. If it is, you could bake the setup to image textures to simplify the material, or you could decide that it’s not worth it if it’s just a small part of the animation that’s slow.
In Cycles, it’s less the polygon count that decides the rendering performance and more the shaders and lighting (especially those visible directly to the camera). If a material that’s really complicated to render takes most of the screen, that’s going to be slow even if the object is just a cube. Meanwhile, a heavy sculpt with 1 million triangles but a simple untextured material would render surprisingly fast.
While I’m on the topic of shader complexity, could the plants be a part of the answer too? If they have translucent materials, I could see them being complicated to render.
In the sampling settings, it’s possible to set a maximum time. Just be careful, this will reduce the quality by cutting the render short. If you can, it’s better to identify the cause of slowness.
I can think of an other explanation, I just don’t know if you have the polygon count for it to be the cause.
I see the object has lots of long bevels and is placed diagonally. That can be a problem in Cycles. Long, narrow faces placed in a diagonal will mess up Cycles’ optimization system.
Cycles relies on the bounding boxes of triangles to decide if a ray might hit a triangle or not. If there is a dense cluster of long, narrow triangles and they are diagonal, their bounding boxes become huge and overlap each other, but the actual faces are small.
If you want, this is something you can test for yourself. Create a bunch of long, narrow cylinders and put them side by side. Do a render and note how long it takes. Then, tilt the cylinders 45 degrees. The render time will be multiplied multiple times.
If you encounter this problem, the solution is to add loop cuts to the object, so the long narrow faces are shortened.
