Rendering is the process of transferring a view on a 3D scene to a 2D image of that scene, according to the position of the viewer. Typically one would use a camera in a 3D computer model to determine the view. The computer can then calculate the 2D image: rendering.
The picture above shows a rendering technique used centuries ago to get the perspective right in 2D sketches. It uses a raster (grid) to get the positions right when transferring the view to the 2D image. You could compare this to the grid of pixels that is used by modern computer renderings. The 'needle' makes sure they eye is always in the same position (moving it, would change the view and thus the image). You could compare it to the camera when rendering a 3D computer model.
From light source to rendered image
In the real world, light travels from lights to the objects we see. It 'bounces' of the surfaces until it finally reaches our eye.
Rendering works in a similar way, but not quite in the same way. First of all, basic rendering doesn't calculate all possible reflections (bounces) of light from all surfaces (which would be a nearly infinite number of light bounces). You'll need advanced render techniques to mimic this light behavior. This is covered in more detail in the Lighting section.
Furthermore light isn't traced into the camera, but the render engine determines which objects (surfaces) are 'in sight' by looking through the camera. The renderer then determines the amount of light that is received by that patch of the surface. This would typically be the direct light received by that surface.
You may see why a renderer works this way: it may take many light paths to be considered to get from the light source, via an object, to the exact position of the camera. Instead it's more efficient to go from the camera to the object and then query the amount of light that gets to that specific patch on the object.
When an image is rendered, this is done in a few basic steps. These are:
1. look through the camera and determine which points in the scene correspond to the pixels in the image that is being rendered;
2. direct light distribution: emit light from all lights and calculate the accumulated intensity for every point in the scene;
3. for each point that needs to be rendered, the shader (material) of the surface is executed to determine the color. This is based on the amount of light this point receives (calculated in the first step) and the properties of the shader.
These basic steps can be expanded with steps for more advanced rendering techniques (such as: reflections, refractions, global- or indirect illumination, caustics, etc).
The model used in Maya for lighting is analogue to the 'real world' physical model, but not identical. There are some fundamental differences. The main reason for most differences is optimization: light can be very complex to calculate. Shortcuts are needed to keep render times as low as possible.
Rendering , het uitrekenen van beelden
Set Render using to Mental Ray.
Setting the render settings
After creating the physical sky for a basic lighting, open your render settings again by clicking the render settings button.
First start with the common settings in the 'common' tab. In the image size settings set the resolution, using one of the presets, to 320x240 for test renderings and to 640x480 or full 1024 for final renders:
Now set the mental ray settings in the 'mental ray' tab. In the anti-aliasing quality setting > Raytrace/Scanline Quality set the sampling with a min sample level of 0 and a max sample level of 2 by sliding the max sample level to 2.
Anti-aliasing quality controls the smoothness of edges in renders. The image below shows the difference between high and low settings of anti-aliasing. High settings improve the quality of the render very much, but will increase render time significantly.
Also in the mental ray tab in the Render Features make sure Raytracing and Final Gathering are enabled.
Rendering and saving an image
Now the settings are setup to make a render. Press the render button to start rendering. The render view will automatically pop up and your image will appear gradually.
When the image is finished rendering you have to save your image to the hard drive to keep it. (maya is finished rendering when the yellow text at the bottom of the render view is replaced with white text showing render details) For saving the image, in the render view you select File > Save image.
You will be asked to define a location and name for the image file. Your are also able to choose an image file type. To maintain the highest image quality choose either Photoshop (*.psd) or Targa (*.tga). The Jpeg file type is also an option, but will result in a low image quality.