feat(gltf): use alternate blending mode for glTF views (#9115)

src/draw/opengles/lv_draw_opengles.c

@@ -626,7 +626,12 @@ static unsigned int create_texture(int32_t w, int32_t h, const void * data)
 #if 0
     GL_CALL(glGenerateMipmap(GL_TEXTURE_2D));
     GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 20));
-    GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST));
+    GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR));
+    /* GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST));
+     * Alternatively, the above form can be used in some cases for slightly faster performance, but
+     * visual quality when using image scales that are not exactly 1:1 (or 2:1 or some other increment)
+     * will be not as good.
+     */
 #endif
 
     GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST));
@@ -658,8 +663,8 @@ static void lv_draw_opengles_3d(lv_draw_task_t * t, const lv_draw_3d_dsc_t * dsc
     lv_area_t clip_area = t->clip_area;
     lv_area_move(&clip_area, -dest_layer->buf_area.x1, -dest_layer->buf_area.y1);
 
-    lv_opengles_render_texture(dsc->tex_id, coords, dsc->opa, targ_tex_w, targ_tex_h, &clip_area, dsc->h_flip,
+    lv_opengles_render(dsc->tex_id, coords, dsc->opa, targ_tex_w, targ_tex_h, &clip_area, dsc->h_flip, !dsc->v_flip,
-                               !dsc->v_flip);
+                       lv_color_black(), true);
 
     if(target_texture) {
         GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER, 0));

src/drivers/opengles/assets/lv_opengles_shader.c

@@ -100,7 +100,7 @@ static const char *src_fragment_shader_v100 = R"(
         }
         if (abs(u_ColorDepth - 8.0) < 0.1) {
             float gray = texColor.r;
-            gl_FragColor = vec4(gray, gray, gray, u_Opa);
+            gl_FragColor = vec4(vec3(gray * u_Opa), u_Opa);
         } else {
             float combinedAlpha = texColor.a * u_Opa;
             gl_FragColor = vec4(texColor.rgb * combinedAlpha, combinedAlpha);
@@ -203,12 +203,16 @@ static const char *src_fragment_shader_v300es = R"(
         if (u_IsFill) {
             texColor = vec4(u_FillColor, 1.0);
         } else {
-            //texColor = texture(u_Texture, v_TexCoord);
+            texColor = texture(u_Texture, v_TexCoord);
-            texColor = textureLod(u_Texture, v_TexCoord, 0.0);  // If the vertices have been transformed, and mipmaps have not been generated, some rotation angles (notably 90 and 270) require using textureLod() to mitigate derivative calculation errors from increments flipping direction
+            /* If the vertices have been transformed, and mipmaps have not been generated, 
+             * some rotation angles (notably 90 and 270) require using textureLod() to mitigate 
+             * derivative calculation errors from interpolator increments flipping direction.
+             * texColor = textureLod(u_Texture, v_TexCoord, u_LodLevel);
+             */
         }
         if (abs(u_ColorDepth - 8.0) < 0.1) {
             float gray = texColor.r;
-            color = vec4(gray, gray, gray, u_Opa);
+            color = vec4(vec3(gray * u_Opa), u_Opa);
         } else {
             float combinedAlpha = texColor.a * u_Opa;
             color = vec4(texColor.rgb * combinedAlpha, combinedAlpha);

src/drivers/opengles/lv_opengles_driver.c

@@ -33,10 +33,9 @@
 /**********************
  *  STATIC PROTOTYPES
  **********************/
-static void lv_opengles_render_internal(unsigned int texture, const lv_area_t * texture_area, lv_opa_t opa,
+
-                                        int32_t disp_w, int32_t disp_h, const lv_area_t * texture_clip_area,
+static void lv_opengles_enable_blending(bool blend_opt);
-                                        bool h_flip, bool v_flip, lv_color_t fill_color);
+static void lv_opengles_disable_blending(void);
-static void lv_opengles_enable_blending(void);
 static void lv_opengles_vertex_buffer_init(const void * data, unsigned int size);
 static void lv_opengles_vertex_buffer_deinit(void);
 static void lv_opengles_vertex_buffer_bind(void);
@@ -102,7 +101,7 @@ void lv_opengles_init(void)
 {
     if(is_init) return;
 
-    lv_opengles_enable_blending();
+    lv_opengles_enable_blending(false);
 
     unsigned int indices[] = {
         0, 1, 2,
@@ -146,15 +145,15 @@ void lv_opengles_render_texture(unsigned int texture, const lv_area_t * texture_
                                 int32_t disp_h, const lv_area_t * texture_clip_area, bool h_flip, bool v_flip)
 {
     LV_PROFILER_DRAW_BEGIN;
-    lv_opengles_render_internal(texture, texture_area, opa, disp_w, disp_h, texture_clip_area, h_flip, v_flip,
+    lv_opengles_render(texture, texture_area, opa, disp_w, disp_h, texture_clip_area, h_flip, v_flip,
-                                lv_color_black());
+                       lv_color_black(), false);
     LV_PROFILER_DRAW_END;
 }
 
 void lv_opengles_render_fill(lv_color_t color, const lv_area_t * area, lv_opa_t opa, int32_t disp_w, int32_t disp_h)
 {
     LV_PROFILER_DRAW_BEGIN;
-    lv_opengles_render_internal(0, area, opa, disp_w, disp_h, area, false, false, color);
+    lv_opengles_render(0, area, opa, disp_w, disp_h, area, false, false, color, false);
     LV_PROFILER_DRAW_END;
 }
 
@@ -210,12 +209,9 @@ void lv_opengles_viewport(int32_t x, int32_t y, int32_t w, int32_t h)
     LV_PROFILER_DRAW_END;
 }
 
-/**********************
+void lv_opengles_render(unsigned int texture, const lv_area_t * texture_area, lv_opa_t opa,
- *   STATIC FUNCTIONS
+                        int32_t disp_w, int32_t disp_h, const lv_area_t * texture_clip_area,
- **********************/
+                        bool h_flip, bool v_flip, lv_color_t fill_color, bool blend_opt)
-
-static void lv_opengles_render_internal(unsigned int texture, const lv_area_t * texture_area, lv_opa_t opa,
-                                        int32_t disp_w, int32_t disp_h, const lv_area_t * texture_clip_area, bool h_flip, bool v_flip, lv_color_t fill_color)
 {
     LV_PROFILER_DRAW_BEGIN;
     lv_area_t intersection;
@@ -263,6 +259,7 @@ static void lv_opengles_render_internal(unsigned int texture, const lv_area_t *
     };
 
     lv_opengles_shader_bind();
+    lv_opengles_enable_blending(blend_opt);
     lv_opengles_shader_set_uniform1f("u_ColorDepth", LV_COLOR_DEPTH);
     lv_opengles_shader_set_uniform1i("u_Texture", 0);
     lv_opengles_shader_set_uniformmatrix3fv("u_VertexTransform", 1, transposed_matrix);
@@ -271,13 +268,23 @@ static void lv_opengles_render_internal(unsigned int texture, const lv_area_t *
     lv_opengles_shader_set_uniform3f("u_FillColor", (float)fill_color.red / 255.0f, (float)fill_color.green / 255.0f,
                                      (float)fill_color.blue / 255.0f);
     lv_opengles_render_draw();
+    lv_opengles_disable_blending();
     LV_PROFILER_DRAW_END;
 }
 
-static void lv_opengles_enable_blending(void)
+/**********************
+ *   STATIC FUNCTIONS
+ **********************/
+
+static void lv_opengles_enable_blending(bool blend_opt)
 {
     GL_CALL(glEnable(GL_BLEND));
-    GL_CALL(glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA));
+    GL_CALL(glBlendFunc(blend_opt ? GL_SRC_ALPHA : GL_ONE, GL_ONE_MINUS_SRC_ALPHA));
+}
+
+static void lv_opengles_disable_blending(void)
+{
+    GL_CALL(glDisable(GL_BLEND));
 }
 
 static void lv_opengles_vertex_buffer_init(const void * data, unsigned int size)

src/drivers/opengles/lv_opengles_driver.h

@@ -45,7 +45,7 @@ void lv_opengles_init(void);
 void lv_opengles_deinit(void);
 
 /**
- * Render a texture
+ * Render a texture using alternate blending mode for smoother translucent materials and correct anti-aliasing of glTF elements when using transparent background
  * @param texture        OpenGL texture ID
  * @param texture_area   the area in the window to render the texture in
  * @param opa            opacity to blend the texture with existing contents

src/drivers/opengles/lv_opengles_private.h

@@ -17,6 +17,9 @@ extern "C" {
 #include "../../lv_conf_internal.h"
 #if LV_USE_OPENGLES
 
+#include "../../misc/lv_area.h"
+#include "../../misc/lv_color.h"
+
 #if LV_USE_EGL
 #include "glad/include/glad/gles2.h"
 #include "glad/include/glad/egl.h"
@@ -100,6 +103,10 @@ extern "C" {
  * GLOBAL PROTOTYPES
  **********************/
 
+void lv_opengles_render(unsigned int texture, const lv_area_t * texture_area, lv_opa_t opa,
+                        int32_t disp_w, int32_t disp_h, const lv_area_t * texture_clip_area,
+                        bool h_flip, bool v_flip, lv_color_t fill_color, bool blend_opt);
+
 /**********************
  *      MACROS
  **********************/