在iOS上使用OpenGL ES 2.0进行实例化绘制 [英] Instanced drawing with OpenGL ES 2.0 on iOS

问题描述

简而言之：

任何人都可以确认是否可以使用内置变量 gl_InstanceID （或 gl_InstanceIDEXT ）在iOS上使用OpenGL ES 2.0且启用了 GL_EXT_draw_instanced 的顶点着色器？

Can anyone confirm whether it is possible to use the built-in variable gl_InstanceID (or gl_InstanceIDEXT) in a vertex shader using OpenGL ES 2.0 on iOS with GL_EXT_draw_instanced enabled?

更长：

我想使用 glDrawArraysInstanced 绘制对象的多个实例和 gl_InstanceID ，我希望我的应用程序能够运行多个平台，包括iOS。

I want to draw multiple instances of an object using glDrawArraysInstanced and gl_InstanceID, and I want my application to run on multiple platforms, including iOS.

规范明确指出这些功能需要ES 3.0。根据 iOS设备兼容性参考 ES 3.0仅适用于少数设备（基于A7 GPU;因此适用于iPhone 5s，但不适用于iPhone 5或更早版本）。

The specification clearly says that these features require ES 3.0. According to the iOS Device Compatibility Reference ES 3.0 is only available on a few devices (those based on the A7 GPU; so iPhone 5s, but not on iPhone 5 or earlier).

所以我的第一个假设是我需要避免在较旧的iOS设备上使用实例绘图。

So my first assumption was that I needed to avoid using instanced drawing on older iOS devices.

然而，进一步向下在兼容性参考文档中，它表示 EXT_draw_instanced 所有SGX Series 5处理器均支持扩展（包括iPhone 5和4s）。

However, further down in the compatibility reference document it says that the EXT_draw_instanced extension is supported for all SGX Series 5 processors (that includes iPhone 5 and 4s).

这让我觉得我确实可以在旧的iOS设备上使用实例绘图，通过查找并使用适当的扩展功能（EXT或ARB）来实现 glDrawArraysInstanced 。

This makes me think that I could indeed use instanced drawing on older iOS devices too, by looking up and using the appropriate extension function (EXT or ARB) for glDrawArraysInstanced.

我目前正在使用 SDL 和 GLEW 所以我还没有在iOS上测试任何东西。

I'm currently just running some test code using SDL and GLEW on Windows so I haven't tested anything on iOS yet.

然而，在我当前的设置中我在使用内置的 gl_InstanceID 时遇到问题顶点着色器中的变量。我收到以下错误消息：

However, in my current setup I'm having trouble using the gl_InstanceID built-in variable in a vertex shader. I'm getting the following error message:

'gl_InstanceID'：变量在当前GLSL版本中不可用

'gl_InstanceID' : variable is not available in current GLSL version

在GLSL中启用draw_instanced扩展名无效：

Enabling the "draw_instanced" extension in GLSL has no effect:

#extension GL_ARB_draw_instanced : enable
#extension GL_EXT_draw_instanced : enable

错误消失时我特别声明我需要ES 3.0（GLSL 300 ES）：

The error goes away when I specifically declare that I need ES 3.0 (GLSL 300 ES):

#version 300 es

虽然在ES 2.0上下文中我的Windows桌面计算机似乎运行正常但我怀疑这适用于iPhone 5。

Although that seem to work fine on my Windows desktop machine in an ES 2.0 context I doubt that this would work on an iPhone 5.

那么，我是否应该放弃能够在较旧的iOS设备上使用实例绘图的想法？

So, shall I abandon the idea of being able to use instanced drawing on older iOS devices?

推荐答案

来自此处：

核心中提供了实例化绘图OpenGL ES 3.0 API和
OpenGL ES 2.0通过EXT_draw_instanced和EXT_instanced_arrays
扩展。

Instanced drawing is available in the core OpenGL ES 3.0 API and in OpenGL ES 2.0 through the EXT_draw_instanced and EXT_instanced_arrays extensions.

您可以看到它们可用于所有GPU，PowerVR SGX，Apple A7，A8。

You can see that it's available on all of their GPUs, PowerVR SGX, Apple A7, A8.

（看起来@ Shammi没有回来......如果他们这样做，你可以改变接受的答案：）

(Looks like @Shammi's not coming back... if they do, you can change the accepted answer :)

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