Porting "Fullscreen" Shaders

[cwkx]

Hi,

I'm porting some work to SFML - I need to apply fullscreen shaders to the entire window render area, instead of just a texture rectangle. I see you can draw shaders by specifying vertices, but after trying:

Code: [Select]


const SF::Vertex vertices[] = { SF::Vertex(SF::Vector2f(-1.0f, 1.0f)), SF::Vertex(SF::Vector2f(1.0f, 1.0f)), SF::Vertex(SF::Vector2f(1.0f, -1.0f)), SF::Vertex(SF::Vector2f(-1.0f, -1.0f)) };
target.draw(&vertices[0], 4, SF::PrimitiveType::Quads, states);

1. I found it doesn't use normalized coords - how can I therefore draw to the entire window render area efficiently (do I really have to recreate 4 vertices from the app size each frame)?

2. I need to use "uniform mat4" for several of my shaders. Do I just do it manually with glUniformMatrix4fv(..., 1, GL_FALSE, &viewMatrix[0][0]); ?

3. I was looking at the code, I noticed setParameter is called in the update loop, which implicitly does: GLint location = glGetUniformLocationARB(m_shaderProgram, name.c_str()); - isn't this slow when you have quite a lot of parameters? What about providing a int getFastParamID(...)  to call in init, then instead of having strings force users who don't care about optimizations to do setParameter(getID("name"), ...) - but this allows users who do care about performance to just send the private GLint from the init - do you think this'll make much difference? (I don't know much about the framework/principles/conventions in SFML yet though so may have missed something)

4. (Offtopic) Is there an easy way to use subpixel font rendering/expose it from freetype? - I haven't looked into this yet.

- P.S. Thanks so much for keeping SFML lightweight! :wink:  I was very happy to see the output size, with static linking, so small.

[Laurent]

1. I found it doesn't use normalized coords - how can I therefore draw to the entire window render area efficiently (do I really have to recreate 4 vertices from the app size each frame)?

Yes. Why is it a problem?

2. I need to use "uniform mat4" for several of my shaders. Do I just do it manually with glUniformMatrix4fv(..., 1, GL_FALSE, &viewMatrix[0][0]); ?

SFML provides support for SFML types. Therefore you can send a sf::Transform (as a mat4), but not a raw matrix. I guess doing it manually would work, although it is not the recommended usage.

3. I was looking at the code, I noticed setParameter is called in the update loop, which implicitly does: GLint location = glGetUniformLocationARB(m_shaderProgram, name.c_str()); - isn't this slow when you have quite a lot of parameters?

Try, and come back with results
My philosophy for SFML is to make it simple, and then only optimize where it is really necessary.
But my guess is that it wouldn't make a big difference.

4. (Offtopic) Is there an easy way to use subpixel font rendering/expose it from freetype? - I haven't looked into this yet.

Easy way, most likely, but "public"/"official", no

[cwkx]

Thanks for the quick reply!

1. Sorry, there's no problem with this at all - I just thought their may have been "GetScreenVertices()" or something - but setting vertices each frame works well:

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const SF::Vertex vertices[] = { SF::Vertex(SF::Vector2f(0.0f, app.getSize().y)), SF::Vertex(SF::Vector2f(app.getSize().x, app.getSize().y)), SF::Vertex(SF::Vector2f(app.getSize().x, 0.0f)), SF::Vertex(SF::Vector2f(0.0f, 0.0f)) };

Simple is good for this library and its intentions

Thanks.

[Laurent]

Do you actually rename namespace sf to SF in your code? :shock: :lol:

[cwkx]

Haha yeah namespace SF = sf; to be consistent with the previous work - thankfully that's the only major change in style though now that your using lowercase camelCase