From f91fdcbdf9dd4ee25fa3c5fc481e12a9ea01504f Mon Sep 17 00:00:00 2001
From: Lars Ivar Hatledal <larsivarhatledal@gmail.com>
Date: Mon, 6 May 2024 22:34:52 +0200
Subject: [PATCH] add functionality for reading texture data back into memory

---
 include/threepp/renderers/GLRenderer.hpp |  3 +++
 src/threepp/renderers/GLRenderTarget.cpp |  2 +-
 src/threepp/renderers/GLRenderer.cpp     | 21 +++++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/threepp/renderers/GLRenderer.hpp b/include/threepp/renderers/GLRenderer.hpp
index ee063257..30eb544b 100644
--- a/include/threepp/renderers/GLRenderer.hpp
+++ b/include/threepp/renderers/GLRenderer.hpp
@@ -152,6 +152,9 @@ namespace threepp {
 
         void readPixels(const Vector2& position, const WindowSize& size, Format format, unsigned char* data);
 
+        // Experimental threepp function
+        void copyTextureToImage(Texture& texture);
+
         void resetState();
 
         void invokeLater(const std::function<void()>& task, float delay = 0);
diff --git a/src/threepp/renderers/GLRenderTarget.cpp b/src/threepp/renderers/GLRenderTarget.cpp
index 6b6c7800..fe888264 100644
--- a/src/threepp/renderers/GLRenderTarget.cpp
+++ b/src/threepp/renderers/GLRenderTarget.cpp
@@ -17,7 +17,7 @@ GLRenderTarget::GLRenderTarget(unsigned int width, unsigned int height, const GL
       scissor(0.f, 0.f, static_cast<float>(width), static_cast<float>(height)),
       viewport(0.f, 0.f, static_cast<float>(width), static_cast<float>(height)),
       depthBuffer(options.depthBuffer), stencilBuffer(options.stencilBuffer), depthTexture(options.depthTexture),
-      texture(Texture::create({})) {
+      texture(Texture::create({Image({}, width, height)})) {
 
     if (options.mapping) texture->mapping = *options.mapping;
     if (options.wrapS) texture->wrapS = *options.wrapS;
diff --git a/src/threepp/renderers/GLRenderer.cpp b/src/threepp/renderers/GLRenderer.cpp
index 08db588a..c90864c1 100644
--- a/src/threepp/renderers/GLRenderer.cpp
+++ b/src/threepp/renderers/GLRenderer.cpp
@@ -1128,6 +1128,22 @@ struct GLRenderer::Impl {
         glReadPixels(static_cast<int>(position.x), static_cast<int>(position.y), size.width, size.width, glFormat, GL_UNSIGNED_BYTE, data);
     }
 
+    void copyTextureToImage(Texture& texture) {
+
+        textures.setTexture2D(texture, 0);
+
+        auto& image = texture.image.front();
+        auto& data = image.data();
+        if (data.empty()) {
+            auto newSize = image.width * image.height * (texture.format == Format::RGB ? 3 : 4);
+            data.resize(newSize);
+        }
+
+        glGetTexImage(GL_TEXTURE_2D, 0, gl::toGLFormat(texture.format), gl::toGLType(texture.type), data.data());
+
+        state.unbindTexture();
+    }
+
     void setViewport(int x, int y, int width, int height) {
 
         _viewport.set(static_cast<float>(x), static_cast<float>(y), static_cast<float>(width), static_cast<float>(height));
@@ -1348,6 +1364,11 @@ void GLRenderer::readPixels(const Vector2& position, const WindowSize& size, For
     pimpl_->readPixels(position, size, format, data);
 }
 
+void GLRenderer::copyTextureToImage(Texture& texture) {
+
+    pimpl_->copyTextureToImage(texture);
+}
+
 void GLRenderer::resetState() {
 
     pimpl_->reset();