Rendering an image

Add at least one light to the scene (see lights and cameras). If you don’t have any lights in the scene the render will come out black.

Once you have lights you can perform test renders of the current view without having to create a camera or render node, but for reproducible results you will want to create a render node and at least one camera. See basic setup for information on setting up a camera and render node.

• Houdini supports doing a “view render” of the current view of the scene using default parameters. This is useful for doing a quick check of render-time effects, shaders, lighting, and so on. You can save the resulting image/animation from the MPlay viewer.

  See the render region tool and starting a render below for how to launch a view render.

• For “real” renders, you will want to create a render node. Render nodes exist in the “Outputs” network (under the /out path in the scene hierarchy). Creating a render node lets you adjust the parameters, such as whether to render a single frame or a sequence, where to render to (MPlay or files on disk), shadows, motion blur, quality, and so on. Where the “view render” renders the current view, a render node requires that you specify a Camera object from which to render.

  See how to set up a render node.

The Launch render button in the toolbox on the left side of the viewer lets you launch a render.

• the button and choose a render output node to render, or View: Mantra to render the current view.

• the button to use the same render output as the last render (the default is a “view render”).

• You can also launch a render by choosing Render > Start Renderer > render node in the main menus.

• If you have a render output node open in a parameter editor, its parameter interface includes a Render button to start rendering the node.

• You can use the render HScript command or the hou.RopNode interface in Python to start a render.

The Render region tool lets you do a quick render of part of the viewer. This lets you quickly check lighting, shaders, motion blur, and so on, without doing a full render.

1. Click the Render Region tool in the toolbox on the left side of the viewer.

2. Drag a rectangle around the area of the viewer you want to render.

   

   • The rendered region will not automatically update, for example when you change a material. Drag the box out again to re-render the region.

   • Select another tool to clear the rendered region.

The “render control” window lets you override certain render node parameters for a single render. This is especially useful for rendering a small number of frames from the full range as a test, without having to edit the render node’s parameters (and remember to put them back afterward).

1. In the main menu, choose Render > Edit Render Node > render node.

2. Click the Render Control button on the parameter editor of the render node.

3. Set the Frame Range option in the Output Overrides section.

You can also override the rendering of dependencies from the window. See [how to set up a render node and the Render Control window for more information.