OpenGL instancing displays strange shapes - c++

Question

I'm making a simple game in OpenGL where there is one player and multiple bubbles, all being spheres. Unfortunately, instancing doesn't work as expected and causes some strange effects. I'm new to instancing and can't see what may be causing a problem.
Draw method in player class:
void Player::draw(glm::mat4 ViewMat, GLfloat aspect, glm::vec3 light, GLfloat zoom)
{
bindProgram();
bindBuffers();
glm::mat4 Projection = glm::perspective(zoom, aspect, 0.1f, 100.0f);
glm::mat4 Model = glm::mat4(1.0f);
glm::mat4 MVP = Projection * ViewMat * Model;
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "MVP"), 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "M"), 1, GL_FALSE, &Model[0][0]);
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "V"), 1, GL_FALSE, &ViewMat[0][0]);
glUniform3f(glGetUniformLocation(shaderProgram, "origin"), origin.x, origin.y, origin.z);
glUniform3f(glGetUniformLocation(shaderProgram, "lightPosWorld"), light.x, light.y, light.z);
glDrawArrays(GL_TRIANGLE_STRIP, 0, vertices.size() / 3);
}
Static draw method in bubble class:
void Bubble::drawAll(glm::mat4 ViewMat, GLfloat aspect, glm::vec3 light, GLfloat zoom,
std::vector<Bubble *> allInstances)
{
std::vector<float> origins;
uint count = 0;
for (auto b : allInstances)
{
origins.push_back(b->origin.x);
origins.push_back(b->origin.y);
origins.push_back(b->origin.z);
count++;
}
allInstances[0]->bindProgram();
allInstances[0]->bindBuffers();
glBufferData(GL_ARRAY_BUFFER, origins.size() * sizeof(origins), origins.data(), GL_STATIC_DRAW);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, originsBuffer);
glVertexAttribPointer(1, // attribute. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void *)0 // array buffer offset
);
glm::mat4 Projection = glm::perspective(zoom, aspect, 0.1f, 100.0f);
glm::mat4 Model = glm::mat4(1.0f);
glm::mat4 MVP = Projection * ViewMat * Model;
GLuint programID = allInstances[0]->shaderProgram;
glVertexAttribDivisor(0, 0);
glVertexAttribDivisor(1, 1);
glUniformMatrix4fv(glGetUniformLocation(programID, "MVP"), 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(glGetUniformLocation(programID, "M"), 1, GL_FALSE, &Model[0][0]);
glUniformMatrix4fv(glGetUniformLocation(programID, "V"), 1, GL_FALSE, &ViewMat[0][0]);
glUniform3f(glGetUniformLocation(programID, "lightPosWorld"), light.x, light.y, light.z);
glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, allInstances[0]->vertices.size() / 3, count);
}
Player vertex shader:
#version 330 core
layout(location = 0) in vec3 vertexPosition_modelspace;
uniform mat4 MVP;
uniform mat4 M;
uniform mat4 V;
uniform vec3 origin;
uniform vec3 lightPosWorld;
uniform vec3 cameraPos;
out vec3 vertexPosWorld;
out vec3 vertexNormal;
out vec3 eyeDirectionCamera;
out vec3 lightDirectionCamera;
void main()
{
gl_Position = MVP * vec4(vertexPosition_modelspace + origin,1);
vertexPosWorld = (M * vec4(vertexPosition_modelspace + origin,1)).xyz;
vertexNormal = normalize(vertexPosWorld - origin);
}
Bubble vertex shader:
#version 330 core
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec3 origin;
uniform mat4 MVP;
uniform mat4 M;
uniform mat4 V;
uniform vec3 lightPosWorld;
uniform vec3 cameraPos;
out vec3 vertexPosWorld;
out vec3 vertexNormal;
out vec3 eyeDirectionCamera;
out vec3 lightDirectionCamera;
void main()
{
gl_Position = MVP * vec4(vertexPosition_modelspace + origin,1);
vertexPosWorld = (M * vec4(vertexPosition_modelspace + origin,1)).xyz;
vertexNormal = normalize(vertexPosWorld - origin);
}
This is what I get:
Effect
But I wanted to get two bubbles that look exactly like the player (which draws correctly).

Answer 1

There are 2 issues in the code:
sizeof(origins) is a byte size of std::vector but not its underlying type. It should be sizeof(float).
glBindBuffer should be called before modifying the buffer’s data and properties.
It should help:
glBindBuffer(GL_ARRAY_BUFFER, originsBuffer);
glBufferData(GL_ARRAY_BUFFER, origins.size() * sizeof(float), origins.data(), GL_STATIC_DRAW);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, // attribute. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void *)0 // array buffer offset
);