# About refraction
**URL:** https://discourse.threejs.org/t/about-refraction/21858
**Category:** Questions
**Tags:** refraction
**Created:** [December 22, 2020, 12:52pm UTC](https://discourse.threejs.org/t/about-refraction/21858 "2020-12-22T12:52:38Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@h\_g\_yan](https://discourse.threejs.org/u/h_g_yan)
#### Post date: [December 22, 2020, 12:52pm UTC](https://discourse.threejs.org/t/about-refraction/21858/1 "2020-12-22T12:52:39Z")
Among the examples of threejs I viewed that are related to refraction, all need a environment map, and the refraction effect is observed through camera directly. I wonder if there are tools available that can focus a spot light, or rectangular area light on a screen, such that the focused area on the screen is brighter than elsewhere. I need to visualize light ray beams before and after the focusing(refraction). I want to use Tyndall effect that purpose, but the effect itself may not be realized with existing tools in threejs.
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### Author:  [@Mugen87](https://discourse.threejs.org/u/Mugen87)
#### Post date: [December 22, 2020, 1:44pm UTC](https://discourse.threejs.org/t/about-refraction/21858/2 "2020-12-22T13:44:51Z")
> [@h\_g\_yan](#):
>
> Among the examples of threejs I viewed that are related to refraction, all need a environment map,
This one does not require an env map: [three.js refraction](https://threejs.org/examples/webgl_refraction)
> [@h\_g\_yan](#):
>
> but the effect itself may not be realized with existing tools in threejs.
Well, `three.js` is just a thin layer above WebGL. As long as you can implement an approach with WebGL, it should be possible with `three.js`, too.
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### Author:  [@h\_g\_yan](https://discourse.threejs.org/u/h_g_yan)
#### Post date: [December 22, 2020, 2:26pm UTC](https://discourse.threejs.org/t/about-refraction/21858/3 "2020-12-22T14:26:40Z")
Thanks for this advice. I thought that example is not real physical refraction. I will study this example in depth.