I am trying to Render a scene with an airplane. I am using Vector Blur AND Motion Blur to get the propeller to look like it’s spinning. To get that effect I have to animate the frame when I render (click Animate button rather then Render/Image) to get motion blur to work. I am using both Vector and Motion blur together as that gives the best effect of a spinning prop.
I have 2 Render Layers setup…one for the propeller only, and one for the rest of the plane. I am trying to animate/render them seperately then coposite them together after rendering.
The Problem: When I select the prop layer, and click the animate button, Blender wants to animate the whole scene for each blur cycle of motion blur (in this case 8 times). That would be fine if it would just render the prop, but it’s rendering both the prop layer and the plane layer thus extending the render times greatly.
The Question: Is there a way I can animate JUST the prop layer to get that spinning prop effect, then render the plane layer seperately? Do have to use mutiple scenes to do this?
I can easily composite them together after each is rendered. Help?
There’s no need to render the animation, rendering the image is just fine. What you do need is to animate the propellers, basically rotate the propellers in between certain frames. Blender with calculate the motion, blur, etc. with rendering only an image.
I tried moving the prop to one scene, and the plane to another scene. Then rendering individually. Problem is with Motion Blur turned on, Blender wants to render both scenes. What am I doing wrong? I want to be able to render the scenes seperately then combine them afterwards with composite.
Motion Blur (as opposed to Vector Blur) will be applied to all objects in any Scene that it’s invoked in, since it is not a Compositor effect. You should be able to limit its use to only one of two Scenes – not sure why that isn’t working for you.
However, as a workaround, you could render the plane (sans Motion Blur) as a separate image. Then in the Scene with just your propellor (you can remove the plane Scene from this file, btw), use an Image node to bring your plane rendering into the Compositor, then a Render Layer containing only the prop & necessary lights & cameras, to place the prop, with Motion and Vector Blur, over the plane image using an Alpha Over node. As long as your plane file & prop file are identical in terms of camera setup, lights, object positioning, etc, it should knit together flawlessly.
Last time i did this the motion blur was best but took to long so I just rendered 1 frame with an ortho camera looking straight at the prop. I then used a slower rotating plane with that motion blurred imaged (alpha) mapped to it.
Still having no luck, but as I am tril and erroring I am having more questions.
Chip, I thought of doing that with an image but then you have the alignment, lighting issues in the event you want to change the camera perspective…doable but more of a pain.
3Point, I am not following what you mean. Can you elaborate?
Attached is a simple blend file showing what I am trying to do. You’ll notice it does render what I want in the end, but it goes through Motion Blur rendering for each scene (the prop and the box), thus extending the render times (in a real application with a much more complex mesh and materials).
Yeah, it kind of assumes you have the scene all ready to go in terms of camera, lights, etc., but that’s true of all “effects” situations. All the composition, camera angle and lighting issues are solved before the elements needed for the effects are produced, so when it’s all assembled, there’s no seams.
Does Motion Blur get applied to objects on hidden Layers as well? Perhaps you could simply render the plane on its own Render Layer in one pass without Motion Blur, with the prop Layer hidden. Then hide the plane Layer(s), reveal the prop Layer, and in the Compositor, Render just the prop Render Layer with Motion Blur enabled. You could save both renders out to RGBA EXR files for compositing. EXR format will retain the alpha channel, so it’s very easy to use the files for post-rendering compositing with Alpha Over.
shoot it from the top with the camera in Ortho (no perspective) and sized to a square that fits the circle of the prop in it.
turn on mblur and render out just 1 frame with an alpha channel
Then you have a blurred see through prop effect to use. Look at some real video of a blurry prop and judge how many revs the blurred version makes.
in the master animation scene, replace the prop with an object/plane, and apply the blurry image (of the propeler) that you just made.
5 animate it rotating slower (at the rate you estimated fdrom the real video).
6 vector blur should work fine with this plane I think.