Will OpenGL ES 2.0 work from under OpenGL ES 3.0?

[VadimBoev]

Version: 1.89.5
Branch: release

Good afternoon dear ImGui. I need to create an Android application that will be based on OpenGL ES 2.0. I found an example for OpenGL ES 3.0, but I also saw in it that you can use ES 2.0. Thus, questions arise:
1.) Will it really work for ES 2.0?
2) Does it guarantee 100% performance on all devices? (because ES 3.0 is not available, as I know, on all phones).
3) Let's say the application is running on OpenGL ES 2.0, but from under OpenGL ES 3.0 (imgui_impl_opengl3.cpp )/ And if the phone does not have OpenGL ES 3, the application will not start?

[VadimBoev]

at the moment I have built an application for OpenGL ES 2.0. Using 'ImGui_ImplOpenGL3_Init("#version 100");' and it works, I will check and test, I will write after a while, can someone share their experience?

[ocornut]

1. 3)imgui_impl_opengl3.cpp supports ES2 you need to #define IMGUI_IMPL_OPENGL_ES2 globally or in your imconfig.h file for it to work, and use GLSL "#version 100" string during init.

Performances should be good, but ES2 doesn't support glDrawElementsBaseVertex() so it may be preferable to also use #define ImDrawIdx unsigned int to use 32-bit indices for large mesh support.

[huguang6]

Hi, there is a question for me, on the arm paltform OpenGL ES 2.0, 32-bit indices is not support and also glDrawElementsBaseVertex(), so how to use "pcmd->VtxOffset" when set flag "ImGuiBackendFlags_RendererHasVtxOffset"

[ocornut]

If it cannot support it then the backend shouldn’t set ImGuiBackendFlags_RendererHasVtxOffset.

[huguang6]

If it cannot support it then the backend shouldn’t set ImGuiBackendFlags_RendererHasVtxOffset.
Thanks! I found the soultion int #3163