Multiple objects drawing (OpenGL) - c++

The issue is that I can't figure out how to properly draw two objects, because my another object isn't being drawn.
Here's the main code:
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);
GLuint VertexArrayID2;
glGenVertexArrays(1, &VertexArrayID2);
glBindVertexArray(VertexArrayID2);
GLuint programID = LoadShaders( "SimpleVertexShader.vertexshader", "SimpleFragmentShader.fragmentshader" );
GLuint MatrixID = glGetUniformLocation(programID, "MVP");
GLuint MatrixID2 = glGetUniformLocation(programID, "MVP2");
glm::mat4 Projection = glm::perspective(45.0f, 5.0f / 4.0f, 0.1f, 100.0f);
glm::mat4 View = glm::lookAt(
glm::vec3(4*2,3*2,8*2),
glm::vec3(0,0,0),
glm::vec3(0,1,0)
);
glm::mat4 Model = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, 0.0f, 0.0f));
glm::mat4 MVP = Projection * View * Model;
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glm::mat4 Model2 = glm::translate(glm::mat4(1.0f), glm::vec3(-5.0f, 0.0f, 0.0f));
glm::mat4 MVP2 = Projection * View * Model2;
glUniformMatrix4fv(MatrixID2, 1, GL_FALSE, &MVP2[0][0]);
static const GLfloat g_vertex_buffer_data[] = {
-1.0f,-1.0f,-1.0f,
-1.0f,-1.0f, 1.0f,
(plenty of floats)
1.0f,-1.0f, 1.0f
};
static const GLfloat g_vertex_buffer_data2[] = {
-1.0f, -1.0f, 3.0f,
(plenty of floats)
0.0f, 1.0f, 2.0f,
};
GLuint vertexbuffer;
glGenBuffers(1, &vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);
GLuint vertexbuffer2;
glGenBuffers(1, &vertexbuffer2);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer2);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data2), g_vertex_buffer_data2, GL_STATIC_DRAW);
do{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(programID);
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(MatrixID2, 1, GL_FALSE, &MVP2[0][0]);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,(void*)0);
glDrawArrays(GL_TRIANGLES, 0, 12*3);
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer2);
glVertexAttribPointer(2,3,GL_FLOAT,GL_FALSE,0,(void*)0);
glDrawArrays(GL_TRIANGLES, 0, 4*3);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(2);
glfwSwapBuffers(window);
glfwPollEvents();
}
And shader:
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 2) in vec3 vertexPosition_modelspace2;
uniform mat4 MVP;
uniform mat4 MVP2;
void main(){
gl_Position = MVP * vec4(vertexPosition_modelspace,1);
gl_Position = MVP2 * vec4(vertexPosition_modelspace2,1);
}
I have noticed that only last object is being drawn, so the issue is that 'gl_Position' overwrites it's values, but how should I figure it out?

gl_Position = MVP * vec4(vertexPosition_modelspace,1);
gl_Position = MVP2 * vec4(vertexPosition_modelspace2,1);
That is not how the graphics pipeline work. You can not draw two objects at the same time. Just the last write to gl_Position will be effective, and your first object will be completely ignored. In the most basic variant, you want to draw two completely independent objects, and you will need two draw calls for that - as you do in your code.
However, when doing so, you do not need two different vertex attributes. Your shader just processes vertices, which in your case only have the verexPosition_modelspace attribute. So you can use that attribute for all the objects you want to draw. There is no point in using different attributes for different objects if the attribute means the same thing.
Let's have a look at your drawing code:
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,(void*)0);
Here, you set up vertex attribute 0 to point to the vertex data of the first buffer, and you enable the attribute array. So the data will not be used as source for vertexPosition_modelspace.
glDrawArrays(GL_TRIANGLES, 0, 12*3);
Now you draw the object. But as we already have seen, your shader does only really use vertexPosition_modelspace2, for which you did not have set an pointer, or enabled the array. Since the array is disabled, the GL will use the current value of attribute 2 - for all vertices. So in the case of triangles, you create triangles with all points being the same - getting triangles with a surface area of 0 and are invisible anyways, no matter what actual value attribute 2 currently has.
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer2);
glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,(void*)0);
Now you do a strange thing: you enable attribute 2 array, but do not set a pointer for it! You should re-specify the pointer for attribute 0 to point to your second model.
glDrawArrays(GL_TRIANGLES, 0, 4*3);
Now you draw with both attribute 0 and 2 enabled. Attribute 0 will contain the data you want, but is ignored by the shader. Attribute 2 is just point somewhere, and you get undefined behavior - it might just crash, but It might also display strange stuff, or nothing at all.
To make this work, just remove vertexPosition_modelspace2 completely from the shader. Use just one MVP matrix also.
When drawing any object, you have to:
Set the MVP uniform matrix for the object
Set the attribute pointer for attribute 0
Enable the attribute array for attribute 0 (or make sure it is already enabled)
Issue the draw call
You can do this with as many objects as you want.

Related

Drawing multiple objects with shaders (GLEW)

I want to draw different figures using triangle fans but I am not sure how to make the program draw the second figure. Do I need a second vertexShaderSource and a second fragmentShaderSource each time I want to change the color or draw a new figure?
Here is the code:
#include <GL/glew.h>
#include <GL/glut.h>
#include <stdio.h>
const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n""void main()\n"
"{\n"
" FragColor = vec4(1.0f, 0.0f, 0.0f, 0.0f);\n" // To set the color.
"}\n\0";
// Set of vertices for the different figures that make up the drawing.
float vertices[] = {
-0.8f, 0.6f, 0.0f, // Center.
-0.8f, 0.4f, 0.0f,
-0.83f, 0.44f, 0.0f,
-0.87f, 0.51f, 0.0f,
-0.9f, 0.57f, 0.0f,
-0.93f, 0.63f, 0.0f,
-0.95f, 0.69f, 0.0f,
-0.97f, 0.75f, 0.0f,
-0.98f, 0.8f, 0.0f,
-0.91f, 0.8f, 0.0f,
-0.85f, 0.79f, 0.0f,
-0.8f, 0.77f, 0.0f,
};
unsigned int VBO, VAO;
GLuint vertexShader;
GLuint fragmentShader;
GLuint shaderProgram;
void display(void){
// Background color.
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLE_FAN, 0, 12);
glBindVertexArray(0);
glFlush();
}
// Main.
int main(int argc, char** argv){
glutInit(&argc, argv);
// Color mode.
glutInitDisplayMode(GLUT_RGBA);
// Window size.
glutInitWindowSize(500, 500);
// Title.
glutCreateWindow("Tarea 3: Figura con curvas");
GLenum err = glewInit();
if(err!=GLEW_OK) {
printf("glewInit failed: %s",glewGetErrorString(err));
exit(1);
}
vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
glutDisplayFunc(display);
glutMainLoop();
}
No is not necessary (or recommended) to use different shaders for the meshes. If you want to draw multiple objects, then you can put the vertex attributes of the meshes to separate Vertex Buffer Objects:
GLuint VBOs[2];
glGenBuffers(2, VBOs);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices_1, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices_2, GL_STATIC_DRAW);
Specify a Vertex Array Object for each mesh:
GLuint VAOs[2];
glGenVertexArrays(2, VAOs);
glBindVertexArray(VAOs[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glBindVertexArray(VAOs[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
Bind the VAO, before the draw call:
glBindVertexArray(VAOs[0]);
glDrawArrays(GL_TRIANGLE_FAN, 0, 12);
glBindVertexArray(VAOs[1]);
glDrawArrays(...);
Of course it is also possible to put all the vertex attributes of the different meshes consecutively in the data store of one VBO. If the vertex specification is identically, then it is event possible to use one single VAO.
Different locations of different meshes can be achieved by vertex transformation in the vertex shader. Use a Uniform of type mat4, to transform the vertices of a mesh:
#version 330 core
layout (location = 0) in vec3 aPos;
uniform mat4 u_model;
void main()
{
gl_Position = u_model * vec4(aPos.xyz, 1.0);
}
See further LearnOpenGL - Transformations.
If the 2 figures are identical, but have just a different location, then you can draw the same mesh twice, but you have to change the model transformation u_model.
You are looking for Uniform buffer objects.
If you have only a single value for a whole draw call, then your shader should be parametrized. The obvious thing you want to parametrize first is the color in the fragment shader, followed by adding a projection matrix to the vertex shader.
From that point onwards it's just alternating between setting new values to uniforms and draw-calls as long as it is the same 3D model.
For different models refer to #rabbid76's answer.

OpenGL 2D projection matrix issue [duplicate]

This question already has an answer here:
Can't set uniform value in OpenGL shader
(1 answer)
Closed 6 years ago.
I have a simple vertex array that draws a quad to the screen.
glViewport(0, 0, screenWidth, screenHeight);
// Load shaders
...
GLfloat vertices[] = {
0.0f, 1.0f,
1.0f, 0.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 1.0f,
1.0f, 0.0f
};
GLuint vao, vbo;
glGenVertexArrays(1, &vao);
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindVertexArray(vao);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), (GLvoid*)0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
...
glUseProgram(program);
glUniform3f(glGetUniformLocation(program, "spriteColour"), colour.x, colour.y, colour.z);
glBindVertexArray(vao);
glDrawArrays(GL_TRIANGLES, 0, 6);
glBindVertexArray(0);
Using the below simple vertex and fragment shaders.
#version 330 core
layout (location = 0) in vec2 vertex;
void main()
{
gl_Position = vec4(vertex.xy, 0.0, 1.0);
}
#version 330 core
out vec4 color;
uniform vec3 spriteColour;
void main()
{
color = vec4(spriteColour, 1.0);
}
This works exactly how I expect. It renders a rectangle to the upper right corner of the window.
Now I want to add a simple model and projection matrix. I am using an orthographic projection matrix and my model matrix just scales the quad to 100 x 100.
glm::mat4 projection = glm::ortho(0.0f, (GLfloat)screenWidth, (GLfloat)screenHeight, 0.0f, -1.0f, 1.0f);
glUniformMatrix4fv(glGetUniformLocation(shader, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
...
glm::mat4 model;
model = glm::scale(model, glm::vec3(100.0f, 100.0f, 1.0f));
glUniformMatrix4fv(glGetUniformLocation(program, "model"), 1, GL_FALSE, glm::value_ptr(model));
...
// Update vertex shader
#version 330 core
layout (location = 0) in vec2 vertex;
uniform mat4 model;
uniform mat4 projection;
void main()
{
gl_Position = projection * model * vec4(vertex.xy, 0.0, 1.0);
}
I would expect this to render a 100 x 100 quad at the top left of the screen however I don't see anything.
I can only assume that somehow my transformations are causing the quad to be drawn off screen and clipped? I am pretty new at Open GL so I am not entirely sure what is wrong here. I've been over it numerous times and based on the tutorials I am using (http://learnopengl.com/) it seems correct.
Does anyone have any ideas as to what I've done wrong?
Turns out you need to activate the program before setting uniforms.
Can't set uniform value in OpenGL shader

Rendering a model in openGL

I'm trying to render this model in openGL:
model in image viewer
this is my attempt so far:
model rendered by my code
I only gave it the verticies so far, no normals or faces. I'm wondering why it doesn't look full like the first one. Is it because of lack of normals? I'm pretty sure I got the number of verticies/triangles right but I'm not sure if I've made mistakes. What is the next step to fully render the model like the first image?
buffer creation:
//Vertex buffer
GLuint vertexbuffer;
glGenBuffers(1, &vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);
//color buffer
GLuint colorbuffer;
glGenBuffers(1, &colorbuffer);
glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);
//create shaders and attach them to a program object
GLuint program = rigShadersToProgram();
GLuint matrixID = glGetUniformLocation(program, "MVP");
rendering loop:
// Rendering loop
while (!glfwWindowShouldClose(window))
{
//clear the screen
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
////////////////////////////matrix operations/////////////////////////////////////////
//projection matrix 45 degree FoV, 4:3 ratio, display range 0.1 - 100
glm::mat4 projection = glm::perspective(99.0f, 4.0f/3.0f, 0.1f, 100.0f);
//camera matrix
glm::mat4 view = glm::lookAt(
glm::vec3(2, 1, -1), //camera is at (2,1,-1)
glm::vec3(0, 0 , 0), //looks at origin
glm::vec3(0,1, 0) //head is up
);
//model matrix identity matrix
glm::mat4 model = glm::mat4(1.0f);
//rotate
model = glm::rotate(model, e, glm::vec3(1,2,3));
//model-view-projection
glm::mat4 MVP = projection * view * model;
//////////////////////////////////////////////////////////////////////////////////////
//use the compiled shaders
glUseProgram(program);
//send transformation matrix to currently bound shader
glUniformMatrix4fv(matrixID, 1, GL_FALSE, &MVP[0][0]);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
//vertex buffer
glVertexAttribPointer(
0, //index
3, //size
GL_FLOAT, //type
GL_FALSE, //normalized?
0, //stride
0 //array buffer offset
);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
//color buffer
glVertexAttribPointer(
1, //index
3, //size
GL_FLOAT, //type
GL_FALSE, //normalized?
0, //stride
0 //array buffer offset
);
//draw triangle
glDrawArrays(GL_TRIANGLES, 0, 12722*3);
std::cout << glfwGetTime() << "\n";
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glfwSwapBuffers(window);
glfwPollEvents();
the model data is stored in an array:
static const GLfloat g_vertex_buffer_data[] = {
-1.557376f, 0.094970f, 0.171995f,
-1.565967f, 0.098142f, 0.171995f,
-1.557376f, 0.094970f, -0.048469f,
-1.565967f, 0.098142f, -0.048469f,
-1.532660f, 0.162907f, -0.048469f,
-1.541251f, 0.166079f, -0.048469f,
-1.444236f, 0.405840f, 0.171996f,
-1.452827f, 0.409013f, 0.171996f,
-1.463533f, 0.352575f, 0.171995f,
-1.472257f, 0.355747f, 0.171995f,
-1.528166f, 0.175331f, 0.011009f,
-1.536757f, 0.178371f, 0.011009f,
-1.538475f, 0.146781f, 0.025019f, ... etc
vertex shader:
#version 430 core
layout(location =0) in vec3 vpos;
layout(location =1) in vec3 vertexColor;
out vec3 fragmentColor;
uniform mat4 MVP;
void main(void)
{
//output position of the vertex in clip space MVP*position
gl_Position = MVP * vec4(vpos,1);
fragmentColor = vertexColor;
};
fragment shader:
#version 430 core
in vec3 fragmentColor;
out vec3 color;
void main()
{
color = fragmentColor;
};
You don't show the actual model loading or rendering code. But what's clear from the screenshot of your program is, that your vertex indexing order is totally messed up. There are vertices connected with each other in your program's drawing that definitely are not connected in the model. Time to recheck the model loader code.
BTW: why did you hardcode the number of vertices to draw in the glDrawArrays call? That doesn't make sense at all.

Issues adding instancing to a working sprite system

I'm trying to implement instancing into my 2d Game Engine so that it can support particle systems without losing any performance. My class, ISprite, is derived from a working Sprite class. I just went through and removed all the functionality affecting single sprites and replaced it with an instancing plan in mind. Unfortunately, nothing is drawing on the screen.
Here is the relevant information:
Vertex Shader
#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec2 texCoords;
layout (location = 2) in vec4 colorSource;
layout (location = 3) in mat4 transform;
out vec2 TexCoords;
out vec4 Color;
uniform mat4 uniformView;
uniform mat4 uniformProjection;
void main()
{
gl_Position = uniformProjection * uniformView * transform * vec4(position, 1.0f);
TexCoords = texCoords;
Color = colorSource;
}
Fragment Shader
#version 330 core
in vec2 TexCoords;
in vec4 Color;
out vec4 color;
uniform sampler2D Texture;
uniform vec4 uniformColor;
void main()
{
vec4 texColor = texture(Texture, TexCoords) * Color;
if(texColor.a < 0.1)
discard;
color = texColor;
}
Load - Prepares all sprites for drawing, called once.
void ISprite::Load(Shader spriteShader)
{
spriteShader.Use();
GLfloat vertices[] = {
//X Y Z
0.5f, -0.5f, 0.0f,
-0.5f, 0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.5f, 0.5f, 0.0f,
-0.5f, 0.5f, 0.0f
};
glGenVertexArrays(1, &vertexArray);
glGenBuffers(1, &positionBuffer);
glGenBuffers(1, &texCoordsBuffer);
glGenBuffers(1, &colorBuffer);
glGenBuffers(1, &matrixBuffer);
glBindVertexArray(vertexArray);
//The vertex data will never change, so send that data now.
glBindBuffer(GL_ARRAY_BUFFER, positionBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//For vertex Position
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(GLfloat), (GLvoid*)0);
//For texture coordinates
glBindBuffer(GL_ARRAY_BUFFER, texCoordsBuffer);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 2*sizeof(GLfloat), (GLvoid*)0);
//For Color
glBindBuffer(GL_ARRAY_BUFFER, colorBuffer);
glEnableVertexAttribArray(2);
glVertexAttribPointer(2, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)0);
//For Transformation Matrix
glBindBuffer(GL_ARRAY_BUFFER, matrixBuffer);
for (int i = 0; i < 4; ++i)
{
glEnableVertexAttribArray(3 + i);
glVertexAttribPointer(3 + i, 4, GL_FLOAT, GL_FALSE,
4 * 4 * sizeof(GLfloat), (GLvoid*)(4 * i * sizeof(GLfloat)));
}
glBindBuffer(GL_ARRAY_BUFFER, positionBuffer);
glBindBuffer(GL_ARRAY_BUFFER, texCoordsBuffer);
glBindBuffer(GL_ARRAY_BUFFER, colorBuffer);
glBindBuffer(GL_ARRAY_BUFFER, matrixBuffer);
glBindVertexArray(0);
glVertexAttribDivisor(positionBuffer, 0);
glVertexAttribDivisor(texCoordsBuffer, 1);
glVertexAttribDivisor(colorBuffer, 1);
glVertexAttribDivisor(matrixBuffer, 1);
glVertexAttribDivisor(matrixBuffer + 1, 1);
glVertexAttribDivisor(matrixBuffer + 2, 1);
glVertexAttribDivisor(matrixBuffer + 3, 1);
ISprite::shader = &spriteShader;
}
Prepare Draw - called by each sprite, each frame. Sends data to static vectors
void ISprite::prepareDraw(void)
{
//Adds their personal data to vectors shared by class
glm::mat4 transform = calculateTransorm();
for (int i = 0; i < 4; ++i)
{
for (int j = 0; j < 4; ++j)
ISprite::transformMatrices.push_back(transform[i][j]);
}
texture.updateAnimation();
for (int i = 0; i < 12; ++i)
ISprite::textureCoordinatesAll.push_back(texture.textureCoordinates[i]);
ISprite::colorValues.push_back(color.x);
ISprite::colorValues.push_back(color.y);
ISprite::colorValues.push_back(color.z);
ISprite::colorValues.push_back(color.w);
}
Draw Sprites - called once each frame, actually draws the sprites
void ISprite::drawSprites(Texture testTexture)
{
shader->Use();
for (std::vector<ISprite*>::iterator it = Isprites.begin(); it != Isprites.end(); ++it)
(*it)->prepareDraw();
glBindVertexArray(vertexArray);
glBindTexture(GL_TEXTURE_2D, testTexture.ID);
//Bind texture here if you want textures to work. if not, a single texture atlas will be bound
glBindBuffer(GL_ARRAY_BUFFER, texCoordsBuffer);
glBufferData(GL_ARRAY_BUFFER, textureCoordinatesAll.size() * sizeof(GLfloat),
textureCoordinatesAll.data(), GL_STREAM_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, colorBuffer);
glBufferData(GL_ARRAY_BUFFER, colorValues.size() * sizeof(GLfloat),
colorValues.data(), GL_STREAM_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, matrixBuffer);
glBufferData(GL_ARRAY_BUFFER, transformMatrices.size() * sizeof(GLfloat),
transformMatrices.data(), GL_STREAM_DRAW);
glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 6, Isprites.size());
textureCoordinatesAll.clear();
colorValues.clear();
transformMatrices.clear();
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindTexture(GL_TEXTURE_2D, 0);
glBindVertexArray(0);
}
There could be a lot of reasons why nothing is rendered. Problems with the transformations, coordinates out of range, etc. But one thing related to instancing definitely looks wrong in the posted code:
glBindVertexArray(0);
glVertexAttribDivisor(positionBuffer, 0);
glVertexAttribDivisor(texCoordsBuffer, 1);
glVertexAttribDivisor(colorBuffer, 1);
...
The first argument to glVertexAttribDivisor() is the location of a vertex attribute, not the name of a buffer. Also, the state set by this call is part of the VAO state, so you should make these calls while the VAO is still bound.
So the calls should look like this:
glVertexAttribDivisor(0, 0);
glVertexAttribDivisor(1, 0);
glVertexAttribDivisor(2, 1);
...
glBindVertexArray(0);
where the first arguments to glVertexAttribDivisor() match the location values you also use as the first argument to glVertexAttribPointer() and glEnableVertexAttribArray().
The divisor value for the texture coordinates (attribute 1) should most likely be 0, since you want the texture coordinates to be set per vertex, just like the positions. For the colors and other remaining attributes, 1 is the correct value so that they are applied per instance.
Also, as I mentioned in a comment, you may also want to look into using point sprites. While they do not offer the same flexibility you can get from drawing individual quads, they can often be used for sprites. With point sprites, you only need one vertex per sprite, and the texture coordinates are generated automatically. My answer here gives an outline on how point sprites are used, including how to apply textures to them: Render large circular points in modern OpenGL.

Drawing Multiple Models in OpenGL 3.x/4.x

I'm working on a rendering engine and so far it's been coming great, but I can not figure out why when I make two drawing calls to render different models, only 1 will show up.
I'm using wxWidgets to handle the window system, the code in question is pasted below. Any suggestions?
Main Rendering Loop
TestShader.Activate();
glUseProgram(TestShader.Program);
ProjectionMatrix = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
int projectionMatrixLocation = glGetUniformLocation(TestShader.Program, "ProjectionMatrix");
glUniformMatrix4fv(projectionMatrixLocation, 1, GL_FALSE, glm::value_ptr(ProjectionMatrix));
glm::mat4 ViewMatrix = glm::lookAt(
glm::vec3(position),
glm::vec3(position+direction),
glm::vec3(up)
);
int viewMatrixLocation = glGetUniformLocation(TestShader.Program, "ViewMatrix");
glUniformMatrix4fv(viewMatrixLocation, 1, GL_FALSE, glm::value_ptr(ViewMatrix));
TestModel[1].Draw(TestShader, glm::vec3(0,0,-11));
TestModel[0].Draw(TestShader, glm::vec3(0,0,-1));
Refresh(false);
Model Drawing Function
void E_MODEL::Draw(EShader Shader, glm::vec3 Location)
{
if (!Registered) glGenVertexArrays(1, &VAO[0]);
glBindVertexArray(VAO[0]);
if (!Registered) glGenBuffers(1, &VBO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
if (!Registered) glBufferData(GL_ARRAY_BUFFER, Vertices.size() * sizeof(glm::vec3), &Vertices[0], GL_STATIC_DRAW);
if (!Registered) glGenBuffers(1, &VBO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
if (!Registered) glBufferData(GL_ARRAY_BUFFER, Normals.size() * sizeof(glm::vec3), &Normals[0], GL_STATIC_DRAW);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
glm::mat4 modelMatrix = glm::translate(glm::mat4(1.0f), Location);
int modelMatrixLocation = glGetUniformLocation(Shader.Program, "modelMatrix");
glUniformMatrix4fv(modelMatrixLocation, 1, GL_FALSE, glm::value_ptr(modelMatrix));
glDrawArrays( GL_TRIANGLES, 0, Vertices.size() );
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glBindVertexArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
Registered = true;
}
Vertex Shader
#version 330 core
// Input vertex data, different for all executions of this shader.
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec3 vertexColor;
// Output data ; will be interpolated for each fragment.
out vec3 fragmentColor;
// Values that stay constant for the whole mesh.
uniform mat4 ProjectionMatrix;
uniform mat4 ViewMatrix;
uniform mat4 modelMatrix;
void main(){
gl_Position = ProjectionMatrix * ViewMatrix * modelMatrix * vec4(vertexPosition_modelspace,1);
// The color of each vertex will be interpolated
// to produce the color of each fragment
fragmentColor = vertexColor;
}
Fragment Shader
#version 330 core
// Interpolated values from the vertex shaders
in vec3 fragmentColor;
// Ouput data
out vec3 color;
void main(){
// Output color = color specified in the vertex shader,
// interpolated between all 3 surrounding vertices
color = fragmentColor;
}
glClear clears a buffer. With the GL_COLOR_BUFFER_BIT flag, you are clearing the color buffer. With the GL_DEPTH_BUFFER_BIT flag, you are clearing the depth buffer. By doing this each time you draw a model, the color and depth information written previously is cleared. This means you are erasing the image every time you draw a model.
You typically clear the buffers once per "paint" or "present". That is, you clear once, you draw N times, you present once. What you are doing now is clear, draw, clear, draw... present.
TL;DR: Call glClear once, before all of your drawing, not before each draw.
is it the glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); inside the draw function? maybe move that out to before you make the calls the draw functions?