I was writing a basic texture batch renderer but somehow, it only renders a single texture rather than four. Is there anything wrong with the below code? I can't find anything wrong with it. I am using GLEW and GLFW for windowing.
The VertexBuffer, VertexArray, IndexBuffer, Shader and Texture classes have been tested and they work correctly.
void BatchRenderObjects(vector<ObjectInstance> texq, GLuint tex_id, Shader shader)
{
int current_index = 0;
int array_index = 0;
const size_t vb_size = 20 * (texq.size());
const size_t ib_size = 6 * texq.size();
const size_t texslot_size = 32;
VertexBuffer VBO(GL_ARRAY_BUFFER);
IndexBuffer IBO;
VertexArray VAO;
GLfloat *vertex_buffer = new GLfloat[vb_size];
GLuint *index_buffer = new GLuint[ib_size];
{
unsigned int offset = 0;
for (int i = 0; i < ib_size; i += 6)
{
index_buffer[i + 0] = 0 + offset;
index_buffer[i + 1] = 1 + offset;
index_buffer[i + 2] = 2 + offset;
index_buffer[i + 3] = 2 + offset;
index_buffer[i + 4] = 3 + offset;
index_buffer[i + 5] = 0 + offset;
offset += 4;
}
}
{
for (int i = 0; i < texq.size(); i++)
{
vertex_buffer[current_index + 0] = texq[i].coords[0];
vertex_buffer[current_index + 1] = texq[i].coords[1];
vertex_buffer[current_index + 2] = texq[i].coords[2];
vertex_buffer[current_index + 3] = texq[i].tex_coords[0];
vertex_buffer[current_index + 4] = texq[i].tex_coords[1];
vertex_buffer[current_index + 5] = texq[i].coords[3];
vertex_buffer[current_index + 6] = texq[i].coords[4];
vertex_buffer[current_index + 7] = texq[i].coords[5];
vertex_buffer[current_index + 8] = texq[i].tex_coords[2];
vertex_buffer[current_index + 9] = texq[i].tex_coords[3];
vertex_buffer[current_index + 10] = texq[i].coords[6];
vertex_buffer[current_index + 11] = texq[i].coords[7];
vertex_buffer[current_index + 12] = texq[i].coords[8];
vertex_buffer[current_index + 13] = texq[i].tex_coords[4];
vertex_buffer[current_index + 14] = texq[i].tex_coords[5];
vertex_buffer[current_index + 15] = texq[i].coords[9];
vertex_buffer[current_index + 16] = texq[i].coords[10];
vertex_buffer[current_index + 17] = texq[i].coords[11];
vertex_buffer[current_index + 18] = texq[i].tex_coords[6];
vertex_buffer[current_index + 19] = texq[i].tex_coords[7];
current_index = current_index + 20;
}
}
// Setup vertex buffer, index buffer and vertex array
{
VAO.Bind();
VBO.BufferData(vb_size, vertex_buffer, GL_STATIC_DRAW);
VBO.VertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
VBO.VertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
IBO.BufferData(ib_size, index_buffer, GL_STATIC_DRAW);
VAO.Unbind();
}
shader.Use();
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex_id);
glUniform1i(glGetUniformLocation(shader.GetProgramID(), "u_Texture"), 0);
VAO.Bind();
glDrawElements(GL_TRIANGLES, 6 * texq.size(), GL_UNSIGNED_INT, 0);
//glDrawArrays(GL_TRIANGLES, 0, 24);
VAO.Unbind();
return;
}
It's actually very basic. It generates a Vertex Buffer and Index Buffer from a structure and draws the texture on the screen. Here is the ObjectInstance structure.
struct ObjectInstance
{
float coords[12];
float tex_coords[8];
};
And finally here is the snippet of my main function.
ObjectInstance t1 = { {-1.0f, -1.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f},
{1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f}};
ObjectInstance t2 = { {-1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, -1.0f, 1.0f, 0.0f},
{1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f}};
ObjectInstance t3 = { {0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f},
{1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f}};
ObjectInstance t4 = { {0.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f},
{1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f}};
std::vector<ObjectInstance> test_vector;
test_vector.push_back(t1);
test_vector.push_back(t2);
test_vector.push_back(t3);
test_vector.push_back(t4);
I call the function with the appropriate arguments in the game loop.
Lastly here is my vertex and fragment shader. VERTEX SHADER :
#version 330 core
layout(location = 0) in vec3 position;
layout(location = 1) in vec2 texCoord;
out vec2 TexCoord;
void main()
{
gl_Position = vec4(position, 1.0f);
TexCoord = texCoord;
}
FRAGMENT SHADER
#version 330 core
in vec2 TexCoord;
out vec4 color; // the color outputted
uniform sampler2D u_Texture;
void main()
{
color = texture(u_Texture, TexCoord);
}
No, I have one texture that I want to draw 4 times. It is just a single texture that I want to draw in different coordinates of the screen. But, apparently I am only getting one of those printed on the bottom-left. Do you have any idea why I am getting this error?
Hey here is the problem.
const size_t vb_size = 20 * (texq.size());
const size_t ib_size = 6 * texq.size();
Should be
const size_t vb_size = (20 * (texq.size())) * sizeof(GLfloat);
const size_t ib_size = (6 * texq.size()) * sizeof(GLfloat);
This is because OpenGL takes the size in raw bytes.