Differences between GLES2 and GLES3¶
This page documents the differences between GLES2 and GLES3 that are by design and are not the result of bugs. There may be differences that are unintentional, but they should be reported as bugs.
Note
"GLES2" and "GLES3" are the names used in Redot for the two OpenGL-based rendering backends. In terms of graphics APIs, the GLES2 backend maps to OpenGL 2.1 on desktop, OpenGL ES 2.0 on mobile and WebGL 1.0 on the web. The GLES3 backend maps to OpenGL 3.3 on desktop, OpenGL ES 3.0 on mobile and WebGL 2.0 on the web.
Particles¶
GLES2 cannot use the Particles or Particles2D nodes as they require advanced GPU features. Instead, use CPUParticles or CPUParticles2D, which provides a similar interface to a ParticlesMaterial.
Tip
Particles and Particles2D can be converted to their CPU equivalent node with the "Convert to CPUParticles" option in the editor.
SCREEN_TEXTURE mip-maps¶
In GLES2, SCREEN_TEXTURE (accessed via a ShaderMaterial) does not have
computed mip-maps. So when accessing at a different LOD, the texture will not appear blurry.
DEPTH_TEXTURE¶
While GLES2 supports DEPTH_TEXTURE in shaders, it may not work on some old hardware (especially mobile).
Color space¶
GLES2 and GLES3 are in different color spaces. This means that colors will appear slightly different between them especially when lighting is used.
If your game is going to use both GLES2 and GLES3, you can use an if
statement check and see if the output is in sRGB, using OUTPUT_IS_SRGB. OUTPUT_IS_SRGB is
true in GLES2 and false in GLES3.
HDR¶
GLES2 is not capable of using High Dynamic Range (HDR) rendering features. If HDR is set for your
project, or for a given viewport, Redot will still use Low Dynamic Range (LDR) which limits
viewport values to the 0-1 range.
The Viewport Debanding property and associated project setting will also have no effect when HDR is disabled. This means debanding can't be used in GLES2.
SpatialMaterial features¶
In GLES2, the following advanced rendering features in the SpatialMaterial are missing:
Refraction
Subsurface scattering
Anisotropy
Clearcoat
Depth mapping
When using SpatialMaterials they will not even appear in the editor.
In custom ShaderMaterials, you can set values for these features but they
will be non-functional. For example, you will still be able to set the SSS built-in (which normally adds
subsurface scattering) in your shader, but nothing will happen.
Environment features¶
In GLES2, the following features in the Environment are missing:
Auto exposure
Tonemapping
Screen space reflections
Screen space ambient occlusion
That means that in GLES2 environments you can only set:
Sky (including procedural sky)
Ambient light
Fog
Depth of field
Glow (also known as bloom)
Adjustment
GIProbes¶
GIProbes do not work in GLES2. Instead use Baked Lightmaps. For a description of how baked lightmaps work see the Baked Lightmaps tutorial.
Contact shadows¶
The shadow_contact property of Lights is not supported in GLES2 and so does nothing.
Light performance¶
In GLES2, performance scales poorly with several lights, as each light is processed in a separate render pass (in opposition to GLES3 which is all done in a single pass). Try to limit scenes to as few lights as possible in order to achieve greatest performance.
Texture compression¶
On mobile, GLES2 requires ETC texture compression, while GLES3 requires ETC2. ETC2 is enabled by default,
so if exporting to mobile using GLES2 make sure to set the project setting
rendering/vram_compression/import_etc and then reimport textures.
Warning
Since ETC doesn't support transparency, you must reimport textures that contain an alpha channel to use the Uncompressed, Lossy or Lossless compression mode (instead of Video RAM). This can be done in the Import dock after selecting them in the FileSystem dock.
Blend shapes¶
In GLES2, blend shapes are implemented on the CPU instead of the GPU. Accordingly, they may not perform as well as blend shapes in GLES3. To avoid performance issues when using blend shapes in GLES2, try to minimize the number of blend shapes that are updated each frame.
Shading language¶
GLES3 provides many built-in functions that GLES2 does not. Below is a list of functions that are not available or are have limited support in GLES2.
For a complete list of built-in GLSL functions see the Shading Language doc.
Function |
|
|---|---|
vec_type modf ( vec_type x, out vec_type i ) |
|
vec_int_type floatBitsToInt ( vec_type x ) |
|
vec_uint_type floatBitsToUint ( vec_type x ) |
|
vec_type intBitsToFloat ( vec_int_type x ) |
|
vec_type uintBitsToFloat ( vec_uint_type x ) |
|
ivec2 textureSize ( sampler2D_type s, int lod ) |
See workaround below |
ivec2 textureSize ( samplerCube s, int lod ) |
See workaround below |
vec4_type texture ( sampler_type s, vec_type uv [, float bias] ) |
bias not available in vertex shader |
vec4_type textureProj ( sampler_type s, vec_type uv [, float bias] ) |
|
vec4_type textureLod ( sampler_type s, vec_type uv, float lod ) |
Only available in vertex shader on some hardware |
vec4_type textureProjLod ( sampler_type s, vec_type uv, float lod ) |
|
vec4_type textureGrad ( sampler_type s, vec_type uv, vec_type dPdx, vec_type dPdy ) |
|
vec_type dFdx ( vec_type p ) |
|
vec_type dFdy ( vec_type p ) |
|
vec_type fwidth ( vec_type p ) |
Note
Functions not in GLES2's GLSL were added with Redots own shader standard library. These functions may perform worse in GLES2 compared to GLES3.
textureSize() workaround¶
GLES2 does not support textureSize(). You can get the size of a texture the old fashioned way by passing in a
uniform with the texture size yourself.
// In the shader:
uniform sampler2D textureName;
uniform vec2 textureName_size;
# In GDScript:
material_name.set_shader_param("textureName", my_texture)
material_name.set_shader_param("textureName_size", my_texture_size)
Built in variables and render modes¶
Redot also provides many built-in variables and render modes. Some cannot be supported in GLES2. Below is a list of built-in variables and render modes that, when written to, will have no effect or could even cause issues when using the GLES2 backend.
Variable / Render Mode |
|---|
|
|
|
|
|
|