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//
// Copyright 2014 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// Based on Simple_Texture2D.c from
// Book: OpenGL(R) ES 2.0 Programming Guide
// Authors: Aaftab Munshi, Dan Ginsburg, Dave Shreiner
// ISBN-10: 0321502795
// ISBN-13: 9780321502797
// Publisher: Addison-Wesley Professional
// URLs: http://safari.informit.com/9780321563835
// http://www.opengles-book.com
#include "SampleApplication.h"
#include "common/vector_utils.h"
#include "texture_utils.h"
#include "util/shader_utils.h"
#include <cstring>
#include <iostream>
#include <vector>
using namespace angle;
class SimpleInstancingSample : public SampleApplication
{
public:
SimpleInstancingSample(int argc, char **argv)
: SampleApplication("SimpleInstancing", argc, argv)
{}
bool initialize() override
{
// init instancing functions
char *extensionString = (char *)glGetString(GL_EXTENSIONS);
if (strstr(extensionString, "GL_ANGLE_instanced_arrays"))
{
mVertexAttribDivisorANGLE =
(PFNGLVERTEXATTRIBDIVISORANGLEPROC)eglGetProcAddress("glVertexAttribDivisorANGLE");
mDrawArraysInstancedANGLE =
(PFNGLDRAWARRAYSINSTANCEDANGLEPROC)eglGetProcAddress("glDrawArraysInstancedANGLE");
mDrawElementsInstancedANGLE = (PFNGLDRAWELEMENTSINSTANCEDANGLEPROC)eglGetProcAddress(
"glDrawElementsInstancedANGLE");
}
if (!mVertexAttribDivisorANGLE || !mDrawArraysInstancedANGLE ||
!mDrawElementsInstancedANGLE)
{
std::cerr << "Unable to load GL_ANGLE_instanced_arrays entry points.";
return false;
}
constexpr char kVS[] = R"(attribute vec3 a_position;
attribute vec2 a_texCoord;
attribute vec3 a_instancePos;
varying vec2 v_texCoord;
void main()
{
gl_Position = vec4(a_position.xyz + a_instancePos.xyz, 1.0);
v_texCoord = a_texCoord;
})";
constexpr char kFS[] = R"(precision mediump float;
varying vec2 v_texCoord;
uniform sampler2D s_texture;
void main()
{
gl_FragColor = texture2D(s_texture, v_texCoord);
})";
mProgram = CompileProgram(kVS, kFS);
if (!mProgram)
{
return false;
}
// Get the attribute locations
mPositionLoc = glGetAttribLocation(mProgram, "a_position");
mTexCoordLoc = glGetAttribLocation(mProgram, "a_texCoord");
mInstancePosLoc = glGetAttribLocation(mProgram, "a_instancePos");
// Get the sampler location
mSamplerLoc = glGetUniformLocation(mProgram, "s_texture");
// Load the texture
mTextureID = CreateSimpleTexture2D();
// Initialize the vertex and index vectors
const GLfloat quadRadius = 0.01f;
mVertices.push_back(Vector3(-quadRadius, quadRadius, 0.0f));
mVertices.push_back(Vector3(-quadRadius, -quadRadius, 0.0f));
mVertices.push_back(Vector3(quadRadius, -quadRadius, 0.0f));
mVertices.push_back(Vector3(quadRadius, quadRadius, 0.0f));
mTexcoords.push_back(Vector2(0.0f, 0.0f));
mTexcoords.push_back(Vector2(0.0f, 1.0f));
mTexcoords.push_back(Vector2(1.0f, 1.0f));
mTexcoords.push_back(Vector2(1.0f, 0.0f));
mIndices.push_back(0);
mIndices.push_back(1);
mIndices.push_back(2);
mIndices.push_back(0);
mIndices.push_back(2);
mIndices.push_back(3);
// Tile thousands of quad instances
for (float y = -1.0f + quadRadius; y < 1.0f - quadRadius; y += quadRadius * 3)
{
for (float x = -1.0f + quadRadius; x < 1.0f - quadRadius; x += quadRadius * 3)
{
mInstances.push_back(Vector3(x, y, 0.0f));
}
}
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
return true;
}
void destroy() override
{
glDeleteProgram(mProgram);
glDeleteTextures(1, &mTextureID);
}
void draw() override
{
// Set the viewport
glViewport(0, 0, getWindow()->getWidth(), getWindow()->getHeight());
// Clear the color buffer
glClear(GL_COLOR_BUFFER_BIT);
// Use the program object
glUseProgram(mProgram);
// Load the vertex position
glVertexAttribPointer(mPositionLoc, 3, GL_FLOAT, GL_FALSE, 0, mVertices.data());
glEnableVertexAttribArray(mPositionLoc);
// Load the texture coordinate
glVertexAttribPointer(mTexCoordLoc, 2, GL_FLOAT, GL_FALSE, 0, mTexcoords.data());
glEnableVertexAttribArray(mTexCoordLoc);
// Load the instance position
glVertexAttribPointer(mInstancePosLoc, 3, GL_FLOAT, GL_FALSE, 0, mInstances.data());
glEnableVertexAttribArray(mInstancePosLoc);
// Enable instancing
mVertexAttribDivisorANGLE(mInstancePosLoc, 1);
// Bind the texture
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, mTextureID);
// Set the sampler texture unit to 0
glUniform1i(mSamplerLoc, 0);
// Do the instanced draw
mDrawElementsInstancedANGLE(GL_TRIANGLES, static_cast<GLsizei>(mIndices.size()),
GL_UNSIGNED_SHORT, mIndices.data(),
static_cast<GLsizei>(mInstances.size()));
}
private:
// Handle to a program object
GLuint mProgram;
// Attribute locations
GLint mPositionLoc;
GLint mTexCoordLoc;
// Sampler location
GLint mSamplerLoc;
// Texture handle
GLuint mTextureID;
// Instance VBO
GLint mInstancePosLoc;
// Loaded entry points
PFNGLVERTEXATTRIBDIVISORANGLEPROC mVertexAttribDivisorANGLE;
PFNGLDRAWARRAYSINSTANCEDANGLEPROC mDrawArraysInstancedANGLE;
PFNGLDRAWELEMENTSINSTANCEDANGLEPROC mDrawElementsInstancedANGLE;
// Vertex data
std::vector<Vector3> mVertices;
std::vector<Vector2> mTexcoords;
std::vector<Vector3> mInstances;
std::vector<GLushort> mIndices;
};
int main(int argc, char **argv)
{
SimpleInstancingSample app(argc, argv);
return app.run();
}
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