Render to texture with explicit call to Update and Render problem

Hi all,

I’m trying to generate images for thumbnails and minimaps.
I have 2 different questions:

1. Can we render a scene to texture and save to image file using headless mode? From what I found, it seems it’s not possible.
2. I rendered my scene using the sample code (in sample.inl)

    // Take screenshot
    else if (key == '9')
    {
        Graphics* graphics = GetSubsystem<Graphics>();
        Image screenshot(context_);
        graphics->TakeScreenShot(screenshot);
        // Here we save in the Data folder with date and time appended
        screenshot.SavePNG(GetSubsystem<FileSystem>()->GetProgramDir() + "Data/Screenshot_" +
            Time::GetTimeStamp().Replaced(':', '_').Replaced('.', '_').Replaced(' ', '_') + ".png");
    }

This code is working just fine. But I have to wait until the scene is rendered and I don’t know when the scene will be rendered. I have to wait for few update loops before it actually drawing the scene.
So I tried calling Renderer’s Update and Render function and then take the screenshot.
This is working but it gives me weird result.

(I’ll post the expected image later because I cannot post 2 images)

It seems to me the there’s a problem with the depth test.
Any idea what’s wrong?
This is my code:

SharedPtr<Viewport> viewport(new Viewport(context_, scene_, cameraNode_->GetComponent<Camera>()));
m_textureOut = new Texture2D(context_);
m_textureOut->SetSize(width, height, Graphics::GetRGBFormat(), TEXTURE_RENDERTARGET);
m_textureOut->SetFilterMode(FILTER_BILINEAR);
RenderSurface* renderSurface = m_textureOut->GetRenderSurface();

renderSurface->SetViewport(0, viewport);
renderSurface->SetUpdateMode(SURFACE_UPDATEALWAYS);
GetSubsystem<Renderer>()->Update(1.0f);
GetSubsystem<Renderer>()->Render();

unsigned char* _ImageData = new unsigned char[m_textureOut->GetDataSize(width, height)];
m_textureOut->GetData(0, _ImageData);
Image* pImage = new Image(context_);
pImage->SetSize(width, height, 3);
pImage->SetData(_ImageData);
pImage->SavePNG("./test.png");

engine_->Exit();

This is the expected result:

Could it be that you are culling the wrong faces? You could try adding <cull value="none" /> to the material and see if that changes it (unless you are certain that it is not the cause – I’ve never experimented with Headless mode so I have nothing to offer if it is something specific to that).

Thanks for the reply.
I tried changing the cullmode, it’s still give the same result.
But I found the problem.

I just need to replace these:

GetSubsystem< Renderer>()->Update(1.0f);
GetSubsystem< Renderer>()->Render();

to

engine_->Update();
engine_->Render();

As far as I’m aware that’s still sane.

This is the code I use for rendering from a lumel for lightmapping:

renderNode_->SetWorldPosition(worldPosition);
Quaternion rotation;
rotation.FromLookRotation(normal);
renderNode_->SetWorldRotation(rotation);

Graphics* graphics = scene->GetSubsystem<Graphics>();
Renderer* renderer = scene->GetSubsystem<Renderer>();

surface_->GetRenderSurface()->QueueUpdate();
graphics->Clear(-1, Color(0, 0, 0));
surface_->GetRenderSurface()->SetViewport(0, viewport_.Get());
renderer->Update();
graphics->SetRenderTarget(0, surface_);
renderer->Render();