2000 2012 Michael O'Rourke Raycast Rendering Maya 2013 (See also the Intro to Lights and Rendering tutorial for an introduction to the basics of rendering an image) Concept There are several algorithms (software approaches) to rendering a picture of 3D scene A common algorithm is raycasting Also known sometimes as scan-line rendering This is Maya s default software rendering approach Maya calls it simply Maya Software Raycasting is simple but gives reasonable results Other rendering algorithms can yield specialized looks For example: vector rendering Other rendering algorithms can yield more physically accurate renderings For example: raytracing and global illumination See the tutorials in this set for each of those renderers Here, we introduce Raycasting The algorithm goes line by line through each pixel of the image
(Hence the term scan-line rendering ) For each pixel of the screen a single beam/ray is cast from the camera location through the pixel until it hits the surface of a model in the scene The ray stops when it hits that surface -- that is, this ray does not bounce off or pass through surfaces This means: It cannot render reflections or refractions at all It can render transparency, but not with 100% physical accuracy To get these effects more accurately, you can use one of the other rendering algorithms Big advantage of raycasting: It can be much faster than raytracing or global illumination, because it is much simpler So If your scene does not require the slower algorithms, you can use the raycasting algorithm Setup Model a simple scene with a few primitives and a floor plane and some lighting
and some shaders Or retrieve an earlier scene Set Parameters for Rendered Picture Before rendering, you should define certain important parameters for the rendering Maya provides default parameters, but here we will set our own values >Window >Rendering Editors >Render Settings Inside the Render Settings window First, at the very top of the window, Make sure Render using is set to Maya Software This is Maya s default and Maya s raycaster Go to the Common tab >File Output > Image Format (Maya.iff,.jpeg,.tiff,.tga, etc) If bringing your file to another program (e.g., Photoshop, Premiere), do NOT use Maya.iff format, since most programs can t read it Leave the rest of the settings as is >Image Size Presets = 640x480 This is a standard video resolution For Digital Video Width = 720, Height = 480 Pixel Aspect Ratio = 0.9 (More about this is the Creating a DV-format Movie tutorial) Go to the Maya Software tab >Anti-aliasing Quality Quality = Preview Quality for testing
Quality = Intermediate for better rendering Other settings may or may not be necessary depending on your situation Leave all other settings in the Render Settings at their defaults Test Render your Frame See the Rendering Test Renders tutorial for details Things you can t do in Raycasting Reflections Make a Phong material In its Attribute Editor, go to >Specular Shading Notice that Reflectivity is 0.5 by default That is 50% reflective Render it as above There are no reflections at all! To get reflections, you must use the raytracing algorithm which is an option within the Maya Software algorithm Refractions This is the bending of light as it passes through a material Classic example: a straw in a glass of water For the same Phong material you made, Look in its Attribute Editor Under the >Raytrace Options tab Again, you have to use raytracing to get this effect Diffuse reflection of light This is the boucing of light off a non-reflective surface For example, off a concrete wall For this effect you need to use either Global illumination or
final gathering (which is a simplified form of global illumination) See the tutorials on those topics for details