Visual rendering

• The only difference between the left and right views should be the viewpoint, not models, textures, colors, and so on (Sections 3.5 and 12.1).
• Never allow words, objects, or images to be fixed to part of the screen; all content should appear to be embedded in the virtual world. Recall from Section 2.1 that being stationary on the screen is not the same as being perceived as stationary in the virtual world.
• Be careful when adjusting the field of view for rendering or any parameters that affect lens distortion that so the result does not cause further mismatch (Sections 7.3 and 12.1).
• Re-evaluate common graphics tricks such as texture mapping and normal mapping, to ensure that they are effective in VR as the user has stereoscopic viewing and is able to quickly change viewpoints (Section 7.2).
• Anti-aliasing techniques are much more critical for VR because of the varying viewpoint and stereoscopic viewing (Section 7.2).
• The rendering system should be optimized so that the desired virtual world can be updated at a frame rate that is at least as high as the hardware requirements (for example, $90$ FPS for Oculus Rift and HTC Vive); otherwise, the frame rate may decrease and vary, which causes discomfort (Section 7.4.)
• Avoid movements of objects that cause most of the visual field to change in the same way; otherwise, the user might feel as if she is moving (Section 8.4).
• Determine how to cull away geometry that is too close to the face of the user; otherwise, substantial vergence-accommodation mismatch will occur (Section 5.4).
• Unlike in games and cinematography, the viewpoint should not change in a way that is not matched to head tracking, unless the intention is for the user to feel as if she is moving in the virtual world, which itself can be uncomfortable (Section 10.2).
• For proper depth and scale perception, the interpupillary distance of the user in the real world should match the corresponding viewpoint distance between eyes in the virtual world (Section 6.1).
• In comparison to graphics on a screen, reduce the brightness and contrast of the models to increase VR comfort.