Create a refractive Material
To create a refractive Material:
- Make sure the Material uses the HDRP Lit Shader.
- In the Surface Options section, set Rendering Pass to Default.
- In the Surface Options section, set Surface Type to Transparent.
- In the Surface Inputs section, select the Base Map color picker, then set Alpha to a value smaller than 1 to make the Material transparent. Or set Base Map to a texture that uses the alpha channel to indicate transparency. A value of 0 means the Material is fully transparent.
- In the Transparency Inputs section, select a Refraction Model other than None.
To create a refractive ShaderGraph:
- Create a Lit Shader Graph.
- In the Graph Inspector, in the Graph Settings tab, in the Surface Options section, set the Surface Type to Transparent. This adds Transparency settings to the Graph Inspector.
- Set Rendering Pass to Default.
- In the Master Stack, set Alpha to a value smaller than 1 to make the Material transparent. A value of 0 means the Material is fully transparent.
- Select a Refraction Model other than None. This adds new properties to the Master Stack.
You can now use the Shader Graph to create a Material that's refractive.
To make refraction more accurate or visible, do the following:
- Set the approximate shape of the object, to make light bend accurately.
- Set the index of refraction, to control how much light bends.
- Set color tint and light absorption.
- Set the smoothness of the material, to control blurriness.
- Add a Reflection Probe, so you see accurate scene colors through the transparent pixels.
- Use an appropriate Proxy Volume shape.
For information on other properties that control refraction, see Surface Type.
Set the approximate shape of the object
Set a refraction model to enable refraction. The refraction model tells HDRP which simple shape most closely matches the internal shape of the object. HDRP uses the shape to calculate how light bends and how far it travels inside the object to the rear surface.
See refraction models for more information about which model to use.
To set the refraction model:
- In a Material's settings, in the Transparency Inputs section, select Refraction Model.
- In Shader Graph, in the Graph Inspector, select Refraction Model.
If you create a Material from a Shader Graph, you can override the Shader Graph refraction model in the Material's settings.
Set the index of refraction
Set the correct index of refraction value for your object's material, so light bends accurately when it enters the object.
The index of refraction defines the ratio between the speed of light in a vacuum and the speed of light in the medium of the Material. HDRP uses this as part of the calculation for how much the light bends.
To set the index of refraction:
- In a Material's settings, in the Transparency Inputs section, set Index of Refraction.
- In Shader Graph, in the Master Stack, set Index of Refraction.
You can use the following physical values, no matter the object shape.
|Index of Refraction (IoR)
|Plastic - plexiglass
|Plastic - polystyrene
Set color tint and light absorption
You can control the color of the refraction effect, and the visibility relative to the object's thickness.
Set the transmission color to control the color tint of the refraction effect. For example for a blue marble, set Transmission Color to blue, because the marble transmits blue light but absorbs other colors.
Set the absorption distance to control when the refraction effect becomes fully colorized by the Transmission Color. Beyond the absorption distance, the object looks darker until it eventually absorbs all the light.
To make sure absorption distance works, use a Transmission Color where the red, green and blue values are below 1.
To set color tint and light absorption:
- In a Material's settings, in the Transparency Inputs section, set Transmission Color and Absorption Distance.
- In Shader Graph, in the Master Stack, input a value or map into Absorption Distance and Transmittance Color.
Materials with the same transmission color but decreasing absorption distance from left to right.
Use a low smoothness value to create a rough surface. Rough surfaces such as a frosted window produce a blurrier refraction effect than smooth surfaces, because microscopic roughness (asperity) spreads the light and reduces its focus.
To set smoothness:
- In a Material's settings, in the Surface Inputs section, set Smoothness.
- In Shader Graph, in the Master Stack, set Smoothness.
Materials with decreasing smoothness from left to right.
Add a Reflection Probe
To create more accurate reflections, place the object inside the Influence Volume of a Reflection Probe.
When a vector leaves the object, it intersects with a point somewhere in the scene.
By default, HDRP uses screen space refraction. This means that HDRP samples the color buffer to find the color at the intersection point. That color becomes the color you see as you look through the transparent pixel on the object.
The color buffer HDRP uses is the first color pyramid that contains only opaque objects, so refractive objects won't be visible through other refractive objects. See Depth pyramid and color pyramid generation in HDRP for more information.
If the intersection point is outside screen space, HDRP tries to fall back to the cubemap texture in a Reflection Probe. If there's no Reflection Probe, HDRP falls back to other sources.
See How HDRP calculates color for reflection and refraction for more information.
Use the Screen Space Refraction override to control how quickly HDRP fades between different sources for the color and avoid visible seams.
Use an appropriate Proxy Volume shape
To create more accurate reflections, check which Proxy Volume the object uses. See Proxy Volume for more information.
If you place the object inside the Influence Volume of a Reflection Probe, HDRP uses the Proxy Volume from the probe. For more information about the size and shape of a Proxy Volume in a probe, see Assign a custom Proxy Volume to a Reflection Probe.
Note: Refraction might not be noticeable if your Material uses the box refraction model and the probe's Proxy Volume uses the Infinite shape.
If the object isn't inside the Influence Volume of a Reflection Probe, HDRP uses the following:
- The Sphere Proxy Volume shape with a 10 meter radius, if the Material uses the sphere refraction model.
- The Infinite Proxy Volume shape, if the Material uses the box refraction model or the thin refraction model.
You might see seams or artifacts on the object, because the shape of the environment usually doesn't exactly match the shape of the Proxy Volume. You should try to use a Proxy Volume shape that matches your environment as closely as possible.
Other types of refraction
You can also use the following:
- Recursive rendering, which allows refractions to include more than one refractive surface per pixel.
- Path tracing, which creates accurate refraction using only indices of refraction and material properties, but is usually too slow for real time rendering because the path tracer casts an actual light path and doesn't approximate shapes or distances.
To disable refraction on all Materials, select Edit > Project Settings > Graphics > HDRP Global Settings > Frame Settings > Rendering and disable Refraction.
If you disable Refraction, refractive Materials fall back to being opaque.