Maya 2012 Tutorial
How to Add Caustics to a Maya Mental Ray Render
When light passes through transparent materials (i.e., water or glass) it is possible to create caustic patterns. You can see this effect on the bottom of a swimming pool on a sunny day or if sunlight passes through a glass of wine. In the wine example, a caustic pattern is cast on the table.
You will also see caustics with reflective surfaces such as jewelry and coins.
Caustics are created by activating light Photons and turning on the caustic option in the Mental Ray Render Settings.
Add a polygon plane to the workspace by choosing Create > Polygon Primitives > Plane.
Add a subdiv cone to the workspace by choosing Create > Subdiv Primitives > Cone.
Using the Move tool (w key) move the cone so it rests on the plane.
Select the Scale tool (r key) and increase the plane so it is several times larger than the cone.
Add an area light to the scene by choosing Create > Lights > Area Light.
Use the Move tool (w key) to position the light behind and slightly above the base of the cone. Press the t key to activate the light's manipulator. Move the manipulator so the light points at the cone.
Select the light and open the light's shape panel in the Attribute Editor.
Open the Mental Ray section, Caustic and Global Illumination section and click the Emit Photons checkbox.
Select the Shadows and Shadow Map Overrides sections in the Mental Ray category. Click the Use Mental Ray Shadow Map Overrides checkbox and choose Detail Shadow Map from the Shadow Map Format pull-down menu. Click the Take Settings from Maya button.
Open the Mental Ray section, Area Light sub-section and check the Use Light Shape checkbox. Increase the High Samples to 30.
Open the Render Settings panel and choose Render Using: Mental Ray.
Click the Quality tab and choose Quality Presets: Production.
Click the Indirect Lighting tab, Caustics section and click the Caustics checkbox.
Select the cone, then right-click the cone and choose Assign New Material > mia_material_x_passes (Mental Ray category).
In the Attribute Editor, mia_material_x_passes tab, click and hold the Presets button and choose GlassPhysical > Replace.
Click the Render Current Frame icon to view your image. You may need to adjust the light intensity value to fine tune the light. Use the Intensity slider to adjust the overall light. To adjust the caustic intensity, change the Photon Intensity value in the light's Caustic and Global Illumination section.
Mental Ray caustic settings can be found in the Render Settings panel, Indirect Lighting tab, Caustics section.
Softer Light Edges
To soften the light edges, select the light and open the Attribute Editor. Adjust the Falloff and Penumbra Angle sliders to create a softer edge.
Shadows too Rough?
To improve the shadow edges, open the light's Attribute Editor settings. In the Mental Ray category, Shadows section, Shadow Map Overrides section, increase the Samples value.
Basic Ray Trace Shadows too Dark?
If you use the light's basic Raytrace shadows and caustics, the object's transparency is omitted in the shadow. If you choose to render using this method, you will need to render using a series of render passes with the caustics turned on and caustics turned off. Your final image is then composited in post production.
Adding Color to your Cone
To change the glass color of your cone, select the cone and open the Attribute Editor, mai_material_x_passes tab. Open the Refraction section and click the Color rectangle.
Can't Find Mental Ray?
If Mental Ray doesn't appear in the Render Settings, Render Using: menu, choose Window > Settings/Preferences > Plug-in Manager. Make sure Mayatomr.bundle is loaded.