Shadeless, Random Image Blender 2.7 Cycles Tutorial
This tutorial is just for SPORT. This is just for ME learning how to work with screencasting. The video is silent as I don't have adequate sound equipment. Moreover, in testing, my voice had a very FLAT AFFECT. I can get animated when talking, but for some reason, talking and concentrating on the tutorial was like not being able to walk and chew gum at the same time. :) Definitely would take practice.
Screencast keys are shown around the bottom left area. I use shortcut keys A LOT. The screencast mouse and keys indicator doesn't show it, but to drag (pan) the scene around without rotating, use Shift + drag mousewheel (MW). To rotate the scene, drag the MW.
The goal of this SILENT tutorial is to randomly select from three images to use on a plane. Each time the plane gets duplicated, it randomly chooses one of the three images as the texture image for the plane. Also, the hue of the images is randomly changed from 0.46 to 0.56 (0.5 is no change). This also demonstrates how to use shadeless rendering in Cycles Render.
I learned the basic idea behind this tutorial from an EnigmaToots tutorial at:
• Video
I really enjoyed that tutorial. However, he has the nodes randomly selecting from two leaf images. I show how to use three images, from which you should get the gist on how to add more images.
Also, randomizing the hue is NOT quite right in his tutorial. I fixed that. He has this logic:
If random less than 0.5, select leaf 2, with hue variation between 0.46 and 0.46 + 0.5 * 0.1 = 0.51. If random greater than or equal to 0.5, select leaf 1, with hue variation between 0.51 and 0.56. The problem is the SAME leaf always gets the SAME hue variation. Each image should get the full random variation in hue between 0.46 and 0.56. Fixed that.
Shadeless rendering of images in Cycles Render, similar to Blender Render / Material context / Shading panel / check Shadeless, I learned from CGCookie here:
http://cgcookie.com/blender/2012/03/0...
Understanding the use of the Mix node as a multiplier, I got that from Amadeo Compositions here:
• Blender Tutorials | First steps and prepar...
The three images I used, a triangle, a square and a circle, are all 640 x 400 pixels. Each image has the same red value = #ff0000. They have a black border, but anything outside of the border has a full alpha value (transparent).
At 0:18 use Ctrl + Alt + U for User Preferences. The word used in the search field is "images". Check "Import Images as Planes", and close User Preferences.
At 2:25 I'm using two "Converter / Math / Less Than" nodes to break up the random value into three ranges, 0.0 to 0.333, 0.333 to 0.666 and 0.666 to 1.0, because there are THREE images. The Random value from the Object Info node ranges between 0.0 and 1.0. The logic is this:
If 0.0 less than or equal to random and random less than 0.333, select image 3.
If 0.333 less than or equal to random and random less than 0.666, select image 2.
If 0.666 less than or equal to random and random less than or equal to 1.0, select image 1.
As regards the hue variation, we cannot just use the Random value in the raw, because the SAME image would have the SAME hue variation. Therefore, we need
If image 1, random = random - 0.666 (leaving range 0.0 to 0.333).
If image 2, random = random - 0.333 (leaving range 0.0 to 0.333).
If image 3, random = random - 0.0 (leaving range 0.0 to 0.333).
This is why the Subtract node is used at 2:56 , where either 0.666, 0.333 or 0.0 is subtracted from random, leaving
0.0 less than or equal to random and less than or equal to 0.333
The resultant range is then multiplied by 0.3 with the "Converter / Math / Multiply" node. That gives a random range from 0.0 to 0.0999. And the result is added to 0.46 to give a full range of random values between 0.46 and 0.46 + 0.0999 = 0.5599, regardless of which image was selected. That's what we wanted.
At 7:39 I screw up with "Shift + Numpad +" so ignore that. I meant to hit "Shift + Numpad Enter" to make the camera view the same size as the rendered image.
At 7:44 and 9:20 hit "F12" key to render scene.