You can set up which pass should be rendered in the Render Global Settings. Maya-Users should know about that!

Transcription

1 Blender as Compositing-Tool Part 1 Single frames Sometimes I miss compositing-utilities in CG-packages like Maya. For simple postproductional compositings Blender is a perfect tool. In this tutorial I show you, how to use it's compositing nodes for a good result. After that I think you will go your own way and have fun to test the possibilities out. 1. Rendering passes f.e. in Maya There are a few ways, to render different passes. These passes have special attributes for a later compositing. Standard passes are Color, Diffuse, Specularity, Shadow and Zdepth. For special purposes you can add for example Ambient Occlusion (AO) and Environment Reflection but sometimes you have to render a seperate layer for it. The passes show exactly one attribute of your rendering. In Specularity you can only see the specular areas of your rendering. In postprocessing you can change their settings for a customized result. You can set up which pass should be rendered in the Render Global Settings. Maya-Users should know about that! In compositing you have to put finaly the passes together. I prefer to render the passes as TIF with Alpha-Channel. 1

2 2. Compositing in Blender Blender involves a nodebased compositing system, which is very comfortable. First I generate a userinterface (UI) that fits for compositing. After starting Blender it looks like this. Delete the cube by push the delete-key on your keyboard. Then you have only to push F10 to get the render-settings at the bottom and change the window-type in the middle by selecting NODE-EDITOR. 2

3 Be sure that COMPOSIT NODES and USE NODES is selected! Now we can start with a simple node network. By right-clicking on the workspace you have the ability to input nodes. ADD INPUT IMAGE load an image of our rendered passes in Blender. LOAD NEW show us the filemanager and we can select the needed image. This you can combine with other nodes (here Bright/Contrast). Add via right-click a new node. It's automaticly connected to the image-node. 3

4 If not, simply drag-and-drop the node-connection from one to the other. For rendering out and preview the compositing you have to add 2 more nodes (output-nodes): ADD OUTPUT COMPOSIT (for rendering) ADD OUTPUT VIEWER (for preview) The preview can be showed after pushing the BACKDROP-button on the bottom of Blender. Change the compositing by changing the values. Just left-click and hold the left mouse-button in the value-field of your node and move it to the left or right. You can also put values in it by left-clicking in the value-field. Now you should see the results in the preview! 4

5 3. Adding your passes In our CG-Tool we rendered out the passes Color, Diffuse, Shadow, Specular and Zdepth. Now we put our passes (here Color and Specular) together. To do this we need a MIX-node (ADD COLOR MIX). The FAC value sets the power of the influence of the added pass or node (here: the second image). In the ADD-menu also other MIX-procedures like Multiply, Darken, Difference can be choosen. Test your settings during compositing by pushing RENDER-button or look at your BACKDROP if activated. 5

6 Are all your passes loaded in the node-network, you will have something this: In addition you can see an AO-pass and nodes for RGB, HUE saturation and bright/contrast. If you have an alpha-relevant pass like the Shadow-pass, combine it by Alpha-Over. In this way the alpha-information gets in your compositing. Our network looks a bit confusing but Blender is able to group nodes. Therefore mark the nodes you want to group (<shift> leftclick) then CTRL+G and ENTER. Notice that you group nodes which are image-nodes as our input-passes! Otherwise you can't see important value-settings anymore! In the final we have a node-network which can manage simple compositing-tasks. 6

7 In the RENDER-settings at the bottom of Blender you can set the file-type (f.e. jpg, tif) for your rendering. The easiest way to get your result is to click on ANIM! Blender renders your compositing and puts it into it's temporary folder. Normaly it's c:\tmp. I hope this is an interesting introduction to Blender as compositing tool. In the following part of this tutorial I will show you how to use Blender for compositing an imagesequence for getting a clip! 7

8 Part 2 Image sequence Blender also is a good tool for compositing image sequences and to get a clip out of it. We have our compositing-network finished and at least we render a whole sequence. Herefore I rendered a little image sequence (about 100 pics) with the passes color, diffuse, shadow and specular. To get your image sequence in your image-nodes just click on your image-node on the button Image- Type. You can see the possibilities Sequence, Movie and Image. Use sequence and load the first image of the sequence like picture1.tif. Now you can see a preview of each frame of the sequence by selecting the frame. But activate the BACKDROP-Button and button for refreshing the preview at frame changes (looks like a car)! For a rendered preview you can also push the RENDER button. It's important to set the number of the start-frame and the amount of the frames to be rendered in the final clip. The amount of images is the value in Frs (frames), the number of the start-frame is called SFra (start frame). 8

9 Now we are ready to go! The important settings for the final step are: 1. choose "Do Composit" and not "Do Sequence"! 2. set start- and end-frame 3. select size and format of the clip (here 1024x768 and AVI); you can also render an image-sequence again by choosing a picture-format like TIF or JPG 4. choose the output-folder Now push the ANIM button. Each frame is shown in Blenders render-window during the renderprocess and the result is put in your output-folder. B. Grünhagen 9