texture_cache: Implement rendering to 3D textures

This allows rendering to 3D textures with more than one slice.
Applications are allowed to render to more than one slice of a texture
using gl_Layer from a VTG shader.

This also requires reworking how 3D texture collisions are handled, for
now, this commit allows rendering to slices but not to miplevels. When a
render target attempts to write to a mipmap, we fallback to the previous
implementation (copying or flushing as needed).

- Fixes color correction 3D textures on UE4 games (rainbow effects).
- Allows Xenoblade games to render to 3D textures directly.

2 files changed, 35 insertions, 20 deletions

diff --git a/src/video_core/renderer_opengl/gl_texture_cache.cpp b/src/video_core/renderer_opengl/gl_texture_cache.cpp
index 57db5a08b..46df15dfc 100644
--- a/src/video_core/renderer_opengl/gl_texture_cache.cpp
+++ b/src/video_core/renderer_opengl/gl_texture_cache.cpp
@@ -263,9 +263,14 @@ CachedSurface::CachedSurface(const GPUVAddr gpu_addr, const SurfaceParams& param
     target = GetTextureTarget(params.target);
     texture = CreateTexture(params, target, internal_format, texture_buffer);
     DecorateSurfaceName();
-    main_view = CreateViewInner(
-        ViewParams(params.target, 0, params.is_layered ? params.depth : 1, 0, params.num_levels),
-        true);
+
+    u32 num_layers = 1;
+    if (params.is_layered || params.target == SurfaceTarget::Texture3D) {
+        num_layers = params.depth;
+    }
+
+    main_view =
+        CreateViewInner(ViewParams(params.target, 0, num_layers, 0, params.num_levels), true);
 }
 
 CachedSurface::~CachedSurface() = default;
@@ -413,20 +418,23 @@ CachedSurfaceView::CachedSurfaceView(CachedSurface& surface, const ViewParams& p
 
 CachedSurfaceView::~CachedSurfaceView() = default;
 
-void CachedSurfaceView::Attach(GLenum attachment, GLenum target) const {
+void CachedSurfaceView::Attach(GLenum attachment, GLenum fb_target) const {
     ASSERT(params.num_levels == 1);
 
+    if (params.target == SurfaceTarget::Texture3D) {
+        if (params.num_layers > 1) {
+            ASSERT(params.base_layer == 0);
+            glFramebufferTexture(fb_target, attachment, surface.texture.handle, params.base_level);
+        } else {
+            glFramebufferTexture3D(fb_target, attachment, target, surface.texture.handle,
+                                   params.base_level, params.base_layer);
+        }
+        return;
+    }
+
     if (params.num_layers > 1) {
-        // Layered framebuffer attachments
         UNIMPLEMENTED_IF(params.base_layer != 0);
-
-        switch (params.target) {
-        case SurfaceTarget::Texture2DArray:
-            glFramebufferTexture(target, attachment, GetTexture(), 0);
-            break;
-        default:
-            UNIMPLEMENTED();
-        }
+        glFramebufferTexture(fb_target, attachment, GetTexture(), 0);
         return;
     }
 
@@ -434,16 +442,16 @@ void CachedSurfaceView::Attach(GLenum attachment, GLenum target) const {
     const GLuint texture = surface.GetTexture();
     switch (surface.GetSurfaceParams().target) {
     case SurfaceTarget::Texture1D:
-        glFramebufferTexture1D(target, attachment, view_target, texture, params.base_level);
+        glFramebufferTexture1D(fb_target, attachment, view_target, texture, params.base_level);
         break;
     case SurfaceTarget::Texture2D:
-        glFramebufferTexture2D(target, attachment, view_target, texture, params.base_level);
+        glFramebufferTexture2D(fb_target, attachment, view_target, texture, params.base_level);
         break;
     case SurfaceTarget::Texture1DArray:
     case SurfaceTarget::Texture2DArray:
     case SurfaceTarget::TextureCubemap:
     case SurfaceTarget::TextureCubeArray:
-        glFramebufferTextureLayer(target, attachment, texture, params.base_level,
+        glFramebufferTextureLayer(fb_target, attachment, texture, params.base_level,
                                   params.base_layer);
         break;
     default:
@@ -500,8 +508,13 @@ OGLTextureView CachedSurfaceView::CreateTextureView() const {
     OGLTextureView texture_view;
     texture_view.Create();
 
-    glTextureView(texture_view.handle, target, surface.texture.handle, format, params.base_level,
-                  params.num_levels, params.base_layer, params.num_layers);
+    if (target == GL_TEXTURE_3D) {
+        glTextureView(texture_view.handle, target, surface.texture.handle, format,
+                      params.base_level, params.num_levels, 0, 1);
+    } else {
+        glTextureView(texture_view.handle, target, surface.texture.handle, format,
+                      params.base_level, params.num_levels, params.base_layer, params.num_layers);
+    }
     ApplyTextureDefaults(surface.GetSurfaceParams(), texture_view.handle);
 
     return texture_view;
diff --git a/src/video_core/renderer_opengl/gl_texture_cache.h b/src/video_core/renderer_opengl/gl_texture_cache.h
index 8a2ac8603..bfc4ddf5d 100644
--- a/src/video_core/renderer_opengl/gl_texture_cache.h
+++ b/src/video_core/renderer_opengl/gl_texture_cache.h
@@ -80,8 +80,10 @@ public:
     explicit CachedSurfaceView(CachedSurface& surface, const ViewParams& params, bool is_proxy);
     ~CachedSurfaceView();
 
-    /// Attaches this texture view to the current bound GL_DRAW_FRAMEBUFFER
-    void Attach(GLenum attachment, GLenum target) const;
+    /// @brief Attaches this texture view to the currently bound fb_target framebuffer
+    /// @param attachment   Attachment to bind textures to
+    /// @param fb_target    Framebuffer target to attach to (e.g. DRAW_FRAMEBUFFER)
+    void Attach(GLenum attachment, GLenum fb_target) const;
 
     GLuint GetTexture(Tegra::Texture::SwizzleSource x_source,
                       Tegra::Texture::SwizzleSource y_source,