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62 lines
2 KiB
Markdown
62 lines
2 KiB
Markdown
## Description
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`gg` is V's simple graphics module.
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It is currently implemented using `sokol`, and makes easy creating
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apps that just need a way to draw simple 2D shapes, and to react to
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user's keyboard/mouse input.
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## Example
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```v cgen
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module main
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import gg
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import gx
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fn main() {
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mut context := gg.new_context(
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bg_color: gx.rgb(174, 198, 255)
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width: 600
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height: 400
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window_title: 'Polygons'
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frame_fn: frame
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)
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context.run()
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}
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fn frame(mut ctx gg.Context) {
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ctx.begin()
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ctx.draw_convex_poly([f32(100.0), 100.0, 200.0, 100.0, 300.0, 200.0, 200.0, 300.0, 100.0, 300.0],
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gx.blue)
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ctx.draw_poly_empty([f32(50.0), 50.0, 70.0, 60.0, 90.0, 80.0, 70.0, 110.0], gx.black)
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ctx.draw_triangle_filled(450, 142, 530, 280, 370, 280, gx.red)
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ctx.end()
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}
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```
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## Troubleshooting
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A common problem, if you draw a lot of primitive elements in the same
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frame, is that there is a chance that your program can exceed the maximum
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allowed amount of vertices and commands, imposed by `sokol`.
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The symptom is that your frame will be suddenly black, after it becomes more complex.
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Sokol's default for vertices is 131072.
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Sokol's default for commands is 32768.
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To solve that, you can try adding these lines at the top of your program:
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`#flag -D_SGL_DEFAULT_MAX_VERTICES=4194304`
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`#flag -D_SGL_DEFAULT_MAX_COMMANDS=65536`
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You can see an example of that in:
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https://github.com/vlang/v/blob/master/examples/gg/many_thousands_of_circles_overriding_max_vertices.v
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Another approach is to use several draw passes, and limit the amount
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of draw calls that you make in each, demonstrated in:
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https://github.com/vlang/v/blob/master/examples/gg/many_thousands_of_circles.v
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Another approach to that problem, is to draw everything yourself in a streaming
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texture, then upload that streaming texture as a single draw command to the GPU.
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You can see an example of that done in:
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https://github.com/vlang/v/blob/master/examples/gg/random.v
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A third approach, is to only upload your changing inputs to the GPU, and do all
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the calculations and drawing there in shaders.
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