I have rendered an object using hdri and lamp lights. Using render layers i want to have object and shadows only. I show you my nodes.  I need to know how to transform white pixels to alpha channel using nodes.
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I am trying to render an animation in cycles without the background. However, every time I have it render, the background still shows up.  I used the compositor to add a background image so I can animate the object around the background. I set the output to RGBA and set the film to transparent.   Now I want to use it in After effects and I simply want to export/render it without the background and make it transparent.  How do I do that?
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I'm trying to make the render have an effect where the stars (which are exploded fragments) have a glowing glare-like effect and the other objects (i.e. film reel and cubes) are their natural colors.  However, despite having made the star objects all a pass index of 1 and the rest 0 by default, everything seems to render a green glowing effect that's supposed to be only for the objects with a pass index of 1.  To illustrate:  This is the render of the image naturally (I rendered at very low quality but it's just for demonstration purposes):    And this is with the composite nodes:    So in essence I want the objects in the the first render I showed to keep those colors, but the stars to have the colors of the green glowing effect.  As you can see from the 2nd picture everything has the green effect.  My node setup is pretty big so I will provide a link to download the  so you can see the nodes more clearly.
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I would like to have my object transparent, with a color only on the edges, would someone know how to do this? I am starting with the nodes, if anyone can help with some guidelines I would really appreciate ;-)  EDIT:  I was looking for something like the hand in Kinectimals :    Thanks
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I am compositing a scene using a standard process in Cycles, and it worked correctly as long as I had my lighting setup in the scene, however when I switched to HDR, my Shadow pass seems to become a solid black. Why is this, and how can it be avoided?  My node setup:
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I have two concentric cubes, both UV-textured, and sharing a material. The outer cube has a texture that is partially transparent.   When I render the scene, the inner cube acts as if the outer cube is fully opaque, and no light falls upon it.  I'd like the outer cube to only cast a shadow for the opaque parts of its texture, rather than all of it.
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I am quite new to Blender. I tried to set up a scene with a little character I modelised with a floor and an hdr. My problem is that the parts of my character which has a reflective material reflect the hdr but not the floor. Here is my viewport with viewport shading. I use eevee.
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In experimenting with an hdr environment texture for the World (with Cycles), I do not see very pronounced shadows in my scene even though the image has an uncloudy sun.  I expect my objects to cast shadows because even though the sky is bright, the sun is much brighter.    For outdoor scenes, is it typical practice to use a Sun lamp in addition to the environment texture or am I missing some other setting?
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I'm trying to render a lightsaber on a transparent background to use as game sprites. I've followed a  on youtube to create the glow/blur effect and it worked great on a black background but it's completely invisible on a transparent background. I figured I had to put an alpha channel node somewhere to make it work but I tried all the "alpha" named nodes all over the place and without success.   This is how the node setup looks like   Here is the  if you want to take a closer look.  EDIT: Found a solution/workaround. Doesn't look as good as before but it's close enough.
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I had accidently deleted the Render Layers and Composite nodes in the Compositing nodes section. When I discovered this problem (as it wouldn't render of course) I re-added those nodes. However now when it renders it only renders the white cap part and not the glass bottle of my scene. Any suggestions please?
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I want to replace the whiteness in pixels with transparency in the same way as described in  - i.e. for lighter pixels to be made proportionally as transparent. All solutions found via google are based on magic wand or other methods that do not work for my needs.  I'm sure there used to be a way to do this in earlier version of Photoshop (a simple functions to replace a colour with transparency), but I can't seem to do it in CS6.  Replace Colour has no alpha options..
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Basically, I would like to make it so that the lighter a pixel is (the more white it has) the more transparent it becomes. Black pixels would be opaque, white pixels would be transparent.  I currently use the slider in blending options on the first tab to get rid of the white and make it transparent but find it works slightly better if I use the magic wand tool with delete.  I figure that there is some blending option out there but there are so many and I'm not sure which to use to achieve my goal.  (Using Photoshop CS6)
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I want to change the color of the shadow casting by a cube to green. While it's very easy to do it in Blender Internal (you select the lamp, go to the Lamp data header and change the shadow's color in the Shadow panel) in Cycles there're no such options. How to achieve it in Cycles?
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In my scene it is required to position the lights close to the main object like this:    How I can make the light source invisible to the camera?
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I'm following this tutorial where you create a popular illusion using images as planes. Tutorial:  However, I can't seem to get the object to receive shadow unlike other objects I've worked with before. It could be that the nodes I've used to get this result is a mix shader that uses the images of the back and front of the illusion with backfacing but I don't know how to get around this.
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I am using the Cycles render engine. I love the ability to use my GPU for rendering, and I have achieved some nice results texture-wise, but I am having a hard time with lighting.   One problem in particular I've noticed is Hemi and Spot lights don't seem to work.   I also don't know what is the most professional way to setup lighting in Blender. I have heard some people say to use planes with an emitter texture for lighting. Does that work better than lamps?
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This questions has already been asked a million times, but nothing solved my issue so far.  Situation   I'm using Blender 2.72b.  I'm not using nodes, just the plain old vanilla settings. But apparently I messed them up somehow. I'm using the Mirror modifier. I'm completely new to blender (and 3D modelling in general) and use it for a couple of days now. I deleted the cube and made this model from scratch (no import).   In texture view everything looks fine:   In material view (and after rendering) everything is black:   Attempts to solve   I have a light source. I have a camera. I have no ceiling. I have a material. I have a texture. Shadows are activated. I tried using nodes and my output was well connected - no change, still black, so I stopped using nodes again (I had no idea what I was doing anyway). I checked out many solutions posted on the web.   As my last attempt, I opened the vanilla start-up file again. Everything works fine with the cube. So I compared the material und texture settings step by step. It all seems the same. This topic is so extraordinary complex and I'm so bloody inexperienced that I'm stuck at this point.
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I have a surface with particles. But I don't want to see the original object in the render. How to fix it?   Transparency, other collection / scene doesn't work.