Draw 2 cubes in OpenGL using GLM - c++

Question

So I can draw a spinning cube using OpenGL3.2+ and translate it away from the 0,0,0 and to the left, but when I try and draw a second one (towards the right), it doesn't render...
This is my display function:
void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(myShader.handle());
GLuint matLocation = glGetUniformLocation(myShader.handle(), "ProjectionMatrix");
glUniformMatrix4fv(matLocation, 1, GL_FALSE, &ProjectionMatrix[0][0]);
spinY+=0.03;
if(spinY>360) spinY = 0;
glm::mat4 viewMatrix;
viewMatrix = glm::translate(glm::mat4(1.0),glm::vec3(0,0,-100)); //viewing matrix
ModelViewMatrix = glm::translate(viewMatrix,glm::vec3(-30,0,0)); //translate object from the origin
ModelViewMatrix = glm::rotate(ModelViewMatrix,spinY, glm::vec3(0,1,0)); //rotate object about y axis
glUniformMatrix4fv(glGetUniformLocation(myShader.handle(), "ModelViewMatrix"), 1, GL_FALSE, &ModelViewMatrix[0][0]); //pass matrix to shader
//Add the following line just before the line to draw the cube to
//check that the origin of the cube in eye space is (-30, 0, -100);
result = glm::vec3(ModelViewMatrix * glm::vec4(0,0,0,1));
std::cout<<glm::to_string(result)<<std::endl; //print matrix to get coordinates.
myCube.render();
glUseProgram(0);
}
I want to be able to use the same Cube class / size etc, but just render it again (I assume that's the most efficient / best way to do it).
I tried this
void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(myShader.handle());
GLuint matLocation = glGetUniformLocation(myShader.handle(), "ProjectionMatrix");
glUniformMatrix4fv(matLocation, 1, GL_FALSE, &ProjectionMatrix[0][0]);
spinY+=0.03;
if(spinY>360) spinY = 0;
glm::mat4 viewMatrix;
viewMatrix = glm::translate(glm::mat4(1.0),glm::vec3(0,0,-100)); //viewing matrix
ModelViewMatrix = glm::translate(viewMatrix,glm::vec3(-30,0,0)); //translate object from the origin
ModelViewMatrix = glm::rotate(ModelViewMatrix,spinY, glm::vec3(0,1,0)); //rotate object about y axis
glUniformMatrix4fv(glGetUniformLocation(myShader.handle(), "ModelViewMatrix"), 1, GL_FALSE, &ModelViewMatrix[0][0]); //pass matrix to shader
//Add the following line just before the line to draw the cube to
//check that the origin of the cube in eye space is (-30, 0, -100);
result = glm::vec3(ModelViewMatrix * glm::vec4(0,0,0,1));
std::cout<<glm::to_string(result)<<std::endl; //print matrix to get coordinates.
myCube.render();
glm::mat4 viewMatrix_TWO;
viewMatrix_TWO = glm::translate(glm::mat4(1.0),glm::vec3(0,0,-100)); //viewing matrix
ModelViewMatrix_TWO = glm::translate(viewMatrix_TWO,glm::vec3(30,0,0)); //translate object from the origin
ModelViewMatrix_TWO = glm::rotate(ModelViewMatrix_TWO,spinY, glm::vec3(0,1,0)); //rotate object about y axis
glUniformMatrix4fv(glGetUniformLocation(myShader.handle(), "ModelViewMatrix_TWO"), 1, GL_FALSE, &ModelViewMatrix[0][0]); //pass matrix to shader
myCube.render();
glUseProgram(0);
}
Obviously, I've implemented it wrong... How can I get a cube either side of the screen? Thanks.
UPDATE
I realised, I hadn't created a second cube object, but with that now implemented, it still doesn't work... Am I confusing how the view/model matrices interact? I've created a new one for each object....
New Code:
myCube.render();
spinX+=0.03;
if(spinX>360) spinX = 0;
glm::mat4 viewMatrix_Two,ModelViewMatrix_Two;
viewMatrix_Two = glm::translate(glm::mat4(1.0),glm::vec3(0,0,-100)); //viewing matrix
ModelViewMatrix_Two = glm::translate(viewMatrix_Two,glm::vec3(30,0,0)); //translate object from the origin
ModelViewMatrix_Two = glm::rotate(ModelViewMatrix_Two,spinX, glm::vec3(0,1,0)); //rotate object about y axis
glUniformMatrix4fv(glGetUniformLocation(myShader.handle(), "ModelViewMatrix_Two"), 1, GL_FALSE, &ModelViewMatrix_Two[0][0]); //pass matrix to shader
myCube_Two.render();
UPDATE
Shader:
uniform mat4 ModelViewMatrix;
//uniform mat4 ModelViewMatrix_Two; //NOT NEEDED - USED SAME SHADER OBJECT
uniform mat4 ProjectionMatrix;
in vec3 in_Position; // Position coming in
in vec3 in_Color; // colour coming in
out vec3 ex_Color; // colour leaving the vertex, this will be sent to the fragment shader
void main(void)
{
gl_Position = ProjectionMatrix * ModelViewMatrix * vec4(in_Position, 1.0);
//gl_Position = ProjectionMatrix * ModelViewMatrix_Two * vec4(in_Position, 1.0);
ex_Color = in_Color;
}

Answer 1

In the end, I created a second Cube object, second viewing matrix and used them with the already established model matrix in my shader seems both cubes are called/rendered individually.
The correct code is:
glm::mat4 viewMatrix_Two, ModelViewMatrix_Two;
viewMatrix_Two = glm::translate(glm::mat4(1.0),glm::vec3(0,0,-200));
ModelViewMatrix = glm::translate(viewMatrix_Two,glm::vec3(30,0,0));
ModelViewMatrix = glm::rotate(ModelViewMatrix,spinX, glm::vec3(1,0,0));
glUniformMatrix4fv(glGetUniformLocation(myShader.handle(), "ModelViewMatrix"), 1, GL_FALSE, &ModelViewMatrix[0][0]); //pass matrix to shader
myCube_Two.render();

Answer 2

Unless your shader has a uniform called ModelViewMatrix_Two, this won't work. I don't see a reason why your shader would need another uniform for the model view since you are not drawing both cube on the same call. If it's not the problem, can you post your shader code?