Using the Hydra Viewer

Katana's Hydra Viewer provides a fast way of previewing geometry, positioning lights and cameras, and exploring the scene graph.

Selecting Objects and Faces

Learn how to select objects and faces for non-destructive manipulation.

In the video:

1.   Click an object to select it then click the Select Faces button to enable Face Selection mode.
2.   Select faces on your object using the marquee tool.
3.   Ctrl + Shift select to add faces.
4.   Shift, click and drag to invert the selection.

The Center of Interest

See how to use the COI to transform lights and cameras.

In the video:

1.   Select a camera and click the COI button to turn on the Center of Interest.
2.   Manipulate the camera manipulators to move the camera, or manipulate the COI to move the camera around the COI.
3.   Select multiple objects to manipulate them with a single COI.

Object vs World Space

Objects can either be transformed in local object space or the global world space.

In the video:

1.   Select and object and click World to move in world space.
2.   Alternatively, click Object to move relative the object's local coordinate system.


You can apply three levels of subdivision to the geometry in the viewer.

In the video:

1.   Select and object and open Edit > Set Subdivision Level to choose a subdivision level. Alternatively use keyboard shortcuts 0, 1, or 2.
2.   You can check the subdivision level using EditSet Subdivision Level.
3.   Multiple object selections can be assigned the same level.

Ambient Occlusion

Apply ambient occlusion for soft shadows in cracks and crevices.

In the video:

1.   Turn on using View > Ambient Occlusion.
2.   Customise using the settings in Edit > Preferences > hydraViewer.

Displaying Textures in the Hydra Viewer

Show .tx or .tex files on objects in the viewer.

In the video:

1.   Add a hydra surface shader to a Material node.
2.   Set the shader to katana_surface and add a texture file.
3.   Drag a material location on to the Parameters tab of a MaterialAssign node.
4.   Add a statement to the parameters and drag the geometry from the scene graph on to the statement.
5.   Add a light to a GafferThree node, and in the node's Material tab, add a hydra light shader.
6.   Select the katana_distant option for the hydra light shader. Adjust the intensity to brighten the scene.

Viewing Proxies and Bounding Boxes

Show simplified proxy geometry and bounding boxes in the viewer.

In the video:

1.   Expand the scene graph to show proxy children.
2.   Use View > Bounding Boxes and View > Proxy Geometry to toggle .
3.   Expand branches in the scene graph to reveal detailed geometry.