Hi,
On 10/07/2016 15:57, Midori Yakumo wrote:
In this QML code:
https://github.com/MidoriYakumo/learnopengl-qt3d/blob/master/qml/hellotriangle.qml
I want to draw a triangle like this C++ code:
http://learnopengl.com/code_viewer.php?code=getting-started/hellotriangle
I found that I have to clear both color and depth buffer, that's weird:
activeFrameGraph:ClearBuffers { buffers: ClearBuffers.ColorDepthBuffer
// Why not ColorBuffer only??? clearColor: Qt.rgba(0.2, 0.3, 0.3, 1.0)
RenderSurfaceSelector { } }
Because by default Qt 3D enables depth testing and writing as this is by
far the most common use case. Thus when you first draw your triangle all
is well as all fragments that get rasterised pass the depth test. On
subsequent frames this is not the case. The default depth test is "less
than" so all your new fragments will fail the depth test and not get
written to the framebuffer and since you already cleared the color
buffer you will see nothing.
Either disable depth testing or just clear the colour and depth buffers
as you are doing. You will likely need depth testing when you progress
on to more complex meshes anyway.
Cheers,
Sean
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