occt render to texture without window

Hi,

I want to use occt + glfw + imgui to program a app.

Here is how I init occt and render 

void OCCTRenderer::initViewer(GLFWwindow* win)
{
	if (m_Display.IsNull())
		m_Display = new Aspect_DisplayConnection;
	Handle(OpenGl_GraphicDriver) aGraphicDriver = new OpenGl_GraphicDriver (m_Display, false);
	Handle(V3d_Viewer) aViewer = new V3d_Viewer (aGraphicDriver);
	aViewer->SetDefaultLights();
	aViewer->SetLightOn();
	aViewer->SetDefaultTypeOfView (V3d_PERSPECTIVE);
	aViewer->ActivateGrid (Aspect_GT_Rectangular, Aspect_GDM_Lines);
	m_View = aViewer->CreateView();
	m_ctx = new OpenGl_Context;
	if (m_ctx->Init(glfwGetWin32Window(win), GetDC(glfwGetWin32Window(win)), glfwGetWGLContext(win))) {
		Handle(OpenGl_FrameBuffer) fbo = new OpenGl_FrameBuffer;
		if (fbo->Init(m_ctx, 800, 600, GL_RGBA8, GL_DEPTH24_STENCIL8)) {
			m_View->View()->SetFBO(fbo);
		    m_Texture = fbo->ColorTexture();
		}
	}
	m_View->SetImmediateUpdate (false);
	m_View->ChangeRenderingParams().ToShowStats = true;
	m_Context = new AIS_InteractiveContext (aViewer);
	m_Context->SetDisplayMode(AIS_Shaded, true);
}

void OCCTRenderer::Render(void)
{
	if (!m_View.IsNull()) {
		m_ctx->MakeCurrent();
		if (m_View->IsInvalidated()){
			m_View->Redraw();
		} else if (m_ToRedraw){
			m_View->RedrawImmediate();
		}
	}
	m_ToRedraw = false;
}

and render like this

    while (!glfwWindowShouldClose(window))
    {
        // Poll and handle events (inputs, window resize, etc.)
        // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
        // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.
        // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
        // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
        glfwPollEvents();

		renderer.Render();

        // Start the Dear ImGui frame
        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();

		renderer.Draw();

        // Rendering
        ImGui::Render();
        int display_w, display_h;
        glfwGetFramebufferSize(window, &display_w, &display_h);
        glViewport(0, 0, display_w, display_h);
        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);


        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
    	
        glfwSwapBuffers(window);
    }

void OCCTRenderer::Draw()
{
	ImGui::SetNextWindowSize(ImVec2(800, 600));
	ImGui::Begin(u8"OCCT Viewer");
	ImGui::Image((ImTextureID)m_Texture->TextureId(), m_Size, ImVec2(0, 1), ImVec2(1, 0));
	ImGui::End();
}

But all I got is a black image.

So, how to render occt into a texture ?

Thanks

trlsmax_152734's picture

Just make it to works.

we still need to pass the glfw window and opengl context to view, so it can init a opengl workspace.

Attachments: 
Daniil Ellovich's picture

Can you share your source code, please? Or maybe somebody can tell how to "pass the glfw window and opengl context to view"?

Kirill Gavrilov's picture

 Daniil Ellovich wrote:

Or maybe somebody can tell how to "pass the glfw window and opengl context to view"?

Have you tried glfw sample coming with OCCT itself?

Frank Martinez's picture

Hi @trlsmax_152734, can you share your working solution?