This is a simple and lightweight OpenGL-based Renderer for my graphics research application. It wraps the GLSL-based Shader to allow quick 3D rendering demostration. GLM(https://github.com/g-truc/glm) is used for matrix calculation.
- Simple: No rendering algorithm is included. You must write yours.
- All the GPU Buffers are allocated at their first usage in rendering.
There are simple examples. I take freeglut as window system in my examples. To use SGLRenderer there are three main steps:
- Writing your glsl-based shader
- initialize Geometry and ShaderMaterial to create a 3D object
- add the 3D object to a Scene.
You must combine the SGLRenderer code with your window system. I think the combination is easy, which only involves initialization and draw code block in Qt and freeglut.
You must name the vertex position attribute in vertex shader as position as the following code shows
in vec3 position;Besides, projection matrix and model-view matrix must be named as projectionMatrix and modelviewMatrix respectively.
uniform mat4 projectionMatrix;
uniform mat4 modelviewMatrix;Projection matrix and model-view matrix will be provided by camera, so you do not need to provide the values for ShaderMaterial.
The complete source code of following examples can be found in the example directory.
This demostrates rendering 3 colorful points. The shader source text is simple.
static const string vs = R"(
#version 130
in vec3 position;
in vec3 color;
uniform mat4 projectionMatrix, modelviewMatrix;
out vec3 u_color;
void main() {
gl_Position = projectionMatrix * modelviewMatrix * vec4(position, 1.0);
u_color = color;
}
)";
static const string fs = R"(
#version 130
in vec3 u_color;
void main(){
gl_FragColor = vec4(u_color,1.0);
}
)";Initialize the 3D object Point.
Ptr<Point> points;
{
vec3 vertex[]={
vec3(-0.5, 0, -100), vec3(0, 0, -100), vec3(0.5, 0, -100)
};
vec3 color[]={
vec3(1,0,0), vec3(0,1,0), vec3(0,0,1)
};
Ptr<VertexBuffer> vbo = VertexBuffer::create(vertex, sizeof(vertex), sizeof(vec3));
Ptr<VertexBuffer> cbo = VertexBuffer::create(color, sizeof(color), sizeof(vec3));
Ptr<Geometry> geometry = Geometry::create();
geometry->add_attribute("position", vbo);
geometry->add_attribute("color", cbo);
Ptr<Shader> shader = Shader::create(vs, fs);
Ptr<ShaderMaterial> material = ShaderMaterial::create(shader);
points = Point::create(geometry, material);
points->set_size(10.f);
}Add points to a scene.
scene = Scene::create();
{
scene->add(points);
}Create a perspective camera.
camera = PerspectiveCamera::create();
{
camera->lookat(vec3(0,0,0),vec3(0,0,-1),vec3(0,1,0));
camera->perspective(atan(1.0/100.0)*2.0, 1.0, 1.0, 1000.0);
}Render the scene.
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
scene->draw(camera.get());Then you can see three colorful points on screen. Your points can be cicle dots. That depends on the GPU driver.
This example shows two colorful lines. The shader source text reads
static const string vs = R"(
#version 130
in vec3 position;
in vec3 color;
uniform mat4 projectionMatrix, modelviewMatrix;
out vec3 u_color;
void main() {
gl_Position = projectionMatrix * modelviewMatrix * vec4(position, 1.0);
u_color = color;
}
)";
static const string fs = R"(
#version 130
in vec3 u_color;
void main(){
gl_FragColor = vec4(u_color,1.0);
}
)";The initialization of 3D object Line has a routine similar to Point.
Ptr<Line> twoLines;
{
vec3 vertex[]={
vec3(0., 0, -100), vec3(0.5, 0, -100), vec3(0.5, 0.5, -100)
};
vec3 color[]={
vec3(1,0,0), vec3(0,1,0), vec3(0,0,1)
};
Ptr<VertexBuffer> vbo = VertexBuffer::create(vertex, sizeof(vertex), sizeof(vec3));
Ptr<VertexBuffer> cbo = VertexBuffer::create(color, sizeof(color), sizeof(vec3));
Ptr<Geometry> geometry = Geometry::create();
geometry->add_attribute("position", vbo);
geometry->add_attribute("color", cbo);
Ptr<Shader> shader = Shader::create(vs, fs);
Ptr<ShaderMaterial> material = ShaderMaterial::create(shader);
twoLines = Line::create(geometry, material);
twoLines->set_line_width(2.0f);
}Add the line instances to a scene and set up a perspective camera.
scene = Scene::create();
{
scene->add(twoLines);
}
camera = PerspectiveCamera::create();
{
camera->lookat(vec3(0,0,0),vec3(0,0,-1),vec3(0,1,0));
camera->perspective(atan(1.0/100.0)*2.0, 1.0, 1.0, 1000.0);
}And render the scene
scene->draw(camera.get());Then we get two orthogonal lines
This example shows the usage of TriMesh. TriMesh is used to render triangles. The data of triangle can be stored as vertices or as vertices and indices.
Shader source:
static const string vs = R"(
#version 130
in vec3 position;
in vec3 color;
uniform mat4 projectionMatrix, modelviewMatrix;
out vec3 u_color;
void main() {
gl_Position = projectionMatrix * modelviewMatrix * vec4(position, 1.0);
u_color = color;
}
)";
static const string fs = R"(
#version 130
in vec3 u_color;
void main(){
gl_FragColor = vec4(u_color,1.0);
}
)";Initialization of TriMesh:
Ptr<TriMesh> triangle;
{
vec3 vertex[]={
vec3(0., 0, -100), vec3(0.5, 0, -100), vec3(0.5, 0.5, -100)
};
vec3 color[]={
vec3(1,0,0), vec3(0,1,0), vec3(0,0,1)
};
Ptr<VertexBuffer> vbo = VertexBuffer::create(vertex, sizeof(vertex), sizeof(vec3));
Ptr<VertexBuffer> cbo = VertexBuffer::create(color, sizeof(color), sizeof(vec3));
Ptr<Geometry> geometry = Geometry::create();
geometry->add_attribute("position", vbo);
geometry->add_attribute("color", cbo);
Ptr<Shader> shader = Shader::create(vs, fs);
Ptr<ShaderMaterial> material = ShaderMaterial::create(shader);
triangle = TriMesh::create(geometry, material);
}Set up scene and camera:
scene = Scene::create();
{
scene->add(triangle);
}
camera = PerspectiveCamera::create();
{
camera->lookat(vec3(0,0,0),vec3(0,0,-1),vec3(0,1,0));
camera->perspective(atan(1.0/100.0)*2.0, 1.0, 1.0, 1000.0);
}And Render the scene:
scene->draw(camera.get());The rendering result shows:
This example shows how to use texture map with Texture2D. The shader reads
static const string vs = R"(
#version 130
in vec3 position;
in vec2 uv;
uniform mat4 projectionMatrix, modelviewMatrix;
out vec2 u_uv;
void main() {
gl_Position = projectionMatrix * modelviewMatrix * vec4(position, 1.0);
u_uv = vec2(uv.x, 1.0 - uv.y);
}
)";
static const string fs = R"(
#version 130
in vec2 u_uv;
uniform sampler2D tex;
void main(){
gl_FragColor = texture(tex, u_uv);
}
)";
Initialize a rectangle and map a texture to this rectangle by the uv coordinates. The initialization of Texture2D is simple as the code block of create-texture-2d shows
Ptr<TriMesh> rect;
{
vec3 vertex[]={
vec3(0., 0, 0), vec3(0.5, 0, 0), vec3(0.5, 0.5, 0), vec3(0., 0.5, 0)
};
vec2 uv[]={
vec2(0,0),vec2(1,0),vec2(1,1),vec2(0,1)
};
unsigned indices[]={0,1,2, 0, 2,3};
Ptr<VertexBuffer> vbo = VertexBuffer::create(vertex, sizeof(vertex), sizeof(vec3));
Ptr<VertexBuffer> uvVBO = VertexBuffer::create(uv, sizeof(uv), sizeof(vec2));
Ptr<IndexBuffer> ibo = IndexBuffer::create(indices, 6);
Ptr<Geometry> geometry = Geometry::create();
geometry->add_attribute("position", vbo);
geometry->add_attribute("uv", uvVBO);
geometry->set_indices(ibo);
Ptr<Shader> shader = Shader::create(vs, fs);
Ptr<ShaderMaterial> material = ShaderMaterial::create(shader);
// create-texture-2d
{
int x, y, ch;
unsigned char *image = stbi_load("../../resouces/skybox/b.jpg", &x, &y, &ch, 3);
assert(image);
Ptr<Texture2D> tex2d = Texture2D::create();
tex2d->set_data(PixelFormat::RGBA,x, y, PixelFormat::RGB, TextureDataType::UBYTE, image);
stbi_image_free(image);
material->set_texture("tex", tex2d);
}
rect = TriMesh::create(geometry, material);
rect->set_position(vec3(0,0,-100));
rect->set_name("rect");
// rect->set_cull_face(Face::Back);
}Like the previous example, set up a scene and camera
scene = Scene::create();
{
scene->add(rect);
}
camera = PerspectiveCamera::create();
{
camera->lookat(vec3(0,0,0),vec3(0,0,-1),vec3(0,1,0));
camera->perspective(atan(1.0/100.0)*2.0, 1.0, 1.0, 1000.0);
}Call the draw method of scene
scene->draw(camera.get());The rendering result shows a picture
