Do Low-Resolution Test Renders

When you're finalizing the look of a model, you often have to make a quick change to the model and render (F12) it to see what it looks like. If you're not careful, you could spend more time waiting for those little test renders than you do actually working on your model.

When you're just doing test previews, these tips can reduce the render time:

• Turn off anti-aliasing. Aliasing is that jaggy stair-stepping that happens around some edges in your renders. Anti-aliasing is the process of trying to smooth those jaggies out. The way anti-aliasing works in Blender is by using a technique known as oversampling, where it renders the same section multiple times and averages out the results to make those edges smoother. Having anti-aliasing enabled is great for final renders, but can really eat up time when you just want to do a quick test. Disable anti-aliasing by left-clicking its check box in the Render Properties.
• Render at reduced size. Most of the time, when you're doing a test, you don't really have to see what the full-size final image will look like. This generalization is especially true if the final render is for print or film, where the final resolution can be greater than 4,000 pixels wide. Of course, you could manually enter a smaller size in the Dimensions section of the Render Properties, but Blender offers a faster way. If you look in the Render Properties, you see a slider under the X and Y resolution values. Adjust this slider to make Blender render your image at that percentage of the final size, thereby reducing the render time for your test preview.
• Turn off computationally intensive features if you don't need them. Features like ambient occlusion (AO), ray tracing, and environmental lighting look great in a final render, but if you're just looking at the form of a model, they aren't necessarily needed for a test. You can turn off ray tracing in the Shading section of the Render Properties. Turning off AO or environmental lighting requires you to go to the World Properties and disable it there.
• Render just the layers you need. If you're working on just one model in a scene and only want to do a test render for that model, disable the layers for other objects in the scene. As long as you have the object and lights in the scene, your test render will be helpful, accurate, and most important, speedy.
• Use the Border Render feature. If you're only interested in doing a test render on a particular part of your scene, switch to the camera view (Numpad 0) and use Border Render by pressing Shift+B and using your mouse cursor to draw a box around the part of the shot you're interested in. When you finish doing tests, you can take this border off by left-clicking the Border check box in the Dimensions section of the Render Properties, or you can press Shift+B and draw a box anywhere outside of the camera's view area.
• If you're animating, use OpenGL previews. In the header of the 3D View, the last button has an icon of a film clapper. Clicking that icon will render your animation, using the same engine that creates the real-time display in the 3D View. In other software, a render that comes from the 3D View is referred to as a playblast. It allows you to see the action and timing of your animation without waiting for all the fancy render settings to kick in. As an additional bonus, I recommend going into the Display section of the Properties region in the 3D View (ViewProperties or press N) and click the Only Render check box before creating your playblast. The Only Render feature hides the extra, nonrendered objects (such as rigs, lights, and the grid plane) in your scene so that you can get a clear playblast without bothersome obstructions.