Reference Render viewer pane

The Render viewer pane renders the scene and automatically updates quickly as you make changes to parameters.

This pane’s viewing interface is nearly identical to the standard image viewer , except that the render viewer cannot show multiple viewports at once. See how to use the image viewer for information on how to work with images in the render viewer.

Toolbar

Re-render	Forces the render view to update now. Ctrl-click this button to re-render any depth and shadow maps.
Stop render	Stops the render if the render view is updating.
Output driver	Choose the output driver (ROP) node with which to render the scene.
Render options	Opens the parameters for the currently selected output driver.
Clear Cache	Clears all saved information the render view uses to speed up re-renders, so the next time you render it will be “from scratch,” without optimizations.
Timeout	The time, in seconds, between when you change a parameter and the render view automatically re-renders the scene.
Create take	Creates a new take with the current render settings. Use this button to “snapshot” different render looks so you can switch back and forth between them. Houdini names the takes starting with `ipr_` followed by a number. You can change the default prefix with the iprview command.

Note

The other toolbars in the render viewer pane are identical to the toolbars of the standard image viewer .

Tasks

To...	Do this
Set up the render viewer pane	See panes for how to set up a takes pane. Use the pop-up menu in the top toolbar to choose the output driver (ROP) to render.
Only update a sub-region of the image	Hold ⇧ Shift and drag a box around the area you want to render. The render view will only update this area. Shift-click without dragging to clear the region.
Save the current render in a take	Click the Create take button on the top toolbar. Houdini saves the rendered image and the settings used to create it in a new take.
Inspect a pixel in the rendered image	Ctrl-click the pixel in the render view. By default, Houdini will print information about the pixel and open the associated object’s shader palette. You can override this behavior by overriding the “pick pixel” script .
Compare the current render to a previous take	Open the difference toolbar . Choose a saved take from the source pop-up menu. Use the controls on the difference toolbar to compare the rendered images.

Warning

Any time you move a light in a scene that uses shadow maps, Ctrl-click the Re-render button to recompute depth and shadow maps.

Add custom functionality to the render viewer

Use the iprview command to set the options of an IPR viewer pane.

Tip

The iprquery and iprquerys expression functions let you query information about the rendered image, such as which shader contributed the pixel at given coordinates. These functions can be very useful for creating custom scripts.

Pick pixel script

When you Ctrl-click in the viewer, Houdini runs the script path/ipr/pickpixel.cmd script. By default, Houdini prints information about the pixel that was picked. If the pixel has a corresponding object, Houdini will open the shader palette for that object’s SHOP.

You can override the default behavior by inserting your own script earlier in the HOUDINI_PATH. Houdini calls the script with three arguments:

The name of the pane where you clicked.
X coordinate of clicked pixel.
Y coordinate of clicked pixel.

Drag and drop script

When you drag an operator onto the viewer, Houdini runs the script path/ipr/dragdrop.cmd script. You can override the default behavior by inserting your own script earlier in the HOUDINI_PATH. Houdini calls the script with five arguments:

The name of the pane where you dropped a node.
X coordinate of the drop.
Y coordinate of the drop.
The type of object dropped:
The name of the dropped object.