rtt,texture: add forward_transforms parameter

This commit changes the default behavior of the render target nodes (rtt,
texture) regarding the camera/model transformations: they are no longer
forwarded to the subgraph unless `forward_transforms` is enabled.

CHANGELOG.md

@@ -21,6 +21,8 @@ Versioning](https://semver.org/spec/v2.0.0.html) for `libnopegl`.
 - `FastGaussianBlur` node to apply a post processing gaussian blur effect to a
   scene that is suitable for real time rendering on mobile devices as well as
   providing a resolution independent blurriness parameter
+- `forward_transforms` parameter to the `Texture` and `RenderToTexture` nodes
+  to enable forwarding of the camera/model transformations
 
 ### Fixed
 - Moving the split position in `ngl-diff`
@@ -39,6 +41,8 @@ Versioning](https://semver.org/spec/v2.0.0.html) for `libnopegl`.
   `ngl_scene_init()` with the associated `ngl_scene_params` structure
 - the `ngl_scene` structure is now private; its parameters can now be obtained
   using `ngl_scene_get_params()`
+- the `Texture` and `RenderToTexture` nodes no longer forward the camera/model
+  transformations by default
 
 ### Removed
 - `%s_dimensions` uniform for 2D array and 3D images/textures, users must use

libnopegl/nodes.specs

@@ -3203,6 +3203,13 @@
           "default": [0.000000,0.000000,0.000000,0.000000],
           "flags": [],
           "desc": "color used to clear the `color_texture`"
+        },
+        {
+          "name": "forward_transforms",
+          "type": "bool",
+          "default": 0,
+          "flags": [],
+          "desc": "enable forwarding of camera/model transformations"
         }
       ]
     },
@@ -3785,6 +3792,13 @@
           "default": [0.000000,0.000000,0.000000,0.000000],
           "flags": [],
           "desc": "color used to clear the texture when used as an implicit render target"
+        },
+        {
+          "name": "forward_transforms",
+          "type": "bool",
+          "default": 0,
+          "flags": [],
+          "desc": "enable forwarding of camera/model transformations when used as an implicit render target"
         }
       ]
     },

libnopegl/src/api.c

@@ -354,6 +354,8 @@ int ngli_ctx_configure(struct ngl_ctx *s, const struct ngl_config *config)
 
     NGLI_ALIGNED_MAT(matrix) = NGLI_MAT4_IDENTITY;
     ngli_gpu_ctx_transform_projection_matrix(s->gpu_ctx, matrix);
+    memcpy(s->default_projection_matrix, matrix, sizeof(matrix));
+
     ngli_darray_clear(&s->projection_matrix_stack);
     if (!ngli_darray_push(&s->projection_matrix_stack, matrix)) {
         ret = NGL_ERROR_MEMORY;
@@ -640,6 +642,9 @@ struct ngl_ctx *ngl_create(void)
     ngli_darray_init(&s->activitycheck_nodes, sizeof(struct ngl_node *), 0);
 
     static const NGLI_ALIGNED_MAT(id_matrix) = NGLI_MAT4_IDENTITY;
+    memcpy(s->default_modelview_matrix, id_matrix, sizeof(id_matrix));
+    memcpy(s->default_projection_matrix, id_matrix, sizeof(id_matrix));
+
     if (!ngli_darray_push(&s->modelview_matrix_stack, id_matrix) ||
         !ngli_darray_push(&s->projection_matrix_stack, id_matrix))
         goto fail;

libnopegl/src/internal.h

@@ -101,6 +101,8 @@ struct ngl_ctx {
     struct rendertarget *available_rendertargets[2];
     struct rendertarget *current_rendertarget;
     int render_pass_started;
+    float default_modelview_matrix[16];
+    float default_projection_matrix[16];
     struct darray modelview_matrix_stack;
     struct darray projection_matrix_stack;
 
@@ -298,6 +300,7 @@ struct texture_opts {
     int direct_rendering;
     int clamp_video;
     float clear_color[4];
+    int forward_transforms;
 };
 
 struct texture_priv {

libnopegl/src/node_rtt.c

@@ -43,6 +43,7 @@ struct rtt_opts {
     struct ngl_node *depth_texture;
     int32_t samples;
     float clear_color[4];
+    int forward_transforms;
 };
 
 struct rtt_priv {
@@ -72,6 +73,8 @@ static const struct node_param rtt_params[] = {
                       .desc=NGLI_DOCSTRING("number of samples used for multisampling anti-aliasing")},
     {"clear_color",   NGLI_PARAM_TYPE_VEC4, OFFSET(clear_color),
                       .desc=NGLI_DOCSTRING("color used to clear the `color_texture`")},
+    {"forward_transforms", NGLI_PARAM_TYPE_BOOL, OFFSET(forward_transforms), {.i32=0},
+                           .desc=NGLI_DOCSTRING("enable forwarding of camera/model transformations")},
     {NULL}
 };
 
@@ -442,6 +445,7 @@ static int rtt_resize(struct ngl_node *node)
 
 static void rtt_draw(struct ngl_node *node)
 {
+    struct ngl_ctx *ctx = node->ctx;
     struct rtt_priv *s = node->priv_data;
     const struct rtt_opts *o = node->opts;
 
@@ -451,9 +455,20 @@ static void rtt_draw(struct ngl_node *node)
             return;
     }
 
+    if (!o->forward_transforms) {
+        if (!ngli_darray_push(&ctx->modelview_matrix_stack, ctx->default_modelview_matrix) ||
+            !ngli_darray_push(&ctx->projection_matrix_stack, ctx->default_projection_matrix))
+            return;
+    }
+
     ngli_rtt_begin(s->rtt_ctx);
     ngli_node_draw(o->child);
     ngli_rtt_end(s->rtt_ctx);
+
+    if (!o->forward_transforms) {
+        ngli_darray_pop(&ctx->modelview_matrix_stack);
+        ngli_darray_pop(&ctx->projection_matrix_stack);
+    }
 }
 
 static void rtt_release(struct ngl_node *node)

libnopegl/src/node_texture.c

@@ -194,6 +194,8 @@ static const struct node_param texture2d_params[] = {
                     .desc=NGLI_DOCSTRING("clamp ngl_texvideo() output to [0;1]")},
     {"clear_color", NGLI_PARAM_TYPE_VEC4, OFFSET(clear_color),
                     .desc=NGLI_DOCSTRING("color used to clear the texture when used as an implicit render target")},
+    {"forward_transforms", NGLI_PARAM_TYPE_BOOL, OFFSET(forward_transforms), {.i32=0},
+                           .desc=NGLI_DOCSTRING("enable forwarding of camera/model transformations when used as an implicit render target")},
     {NULL}
 };
 
@@ -556,6 +558,7 @@ static int rtt_resize(struct ngl_node *node)
 
 static void texture_draw(struct ngl_node *node)
 {
+    struct ngl_ctx *ctx = node->ctx;
     struct texture_priv *s = node->priv_data;
     struct texture_opts *o = node->opts;
 
@@ -568,9 +571,20 @@ static void texture_draw(struct ngl_node *node)
             return;
     }
 
+    if (!o->forward_transforms) {
+        if (!ngli_darray_push(&ctx->modelview_matrix_stack, ctx->default_modelview_matrix) ||
+            !ngli_darray_push(&ctx->projection_matrix_stack, ctx->default_projection_matrix))
+            return;
+    }
+
     ngli_rtt_begin(s->rtt_ctx);
     ngli_node_draw(o->data_src);
     ngli_rtt_end(s->rtt_ctx);
+
+    if (!o->forward_transforms) {
+        ngli_darray_pop(&ctx->modelview_matrix_stack);
+        ngli_darray_pop(&ctx->projection_matrix_stack);
+    }
 }
 
 static void texture_release(struct ngl_node *node)

tests/benchmark.py

@@ -311,6 +311,7 @@ def _get_random_layer(cfg: ngl.SceneCfg, rng, t0, t1, enable_computes, layer=4):
             rtt = ngl.RenderToTexture(
                 child,
                 clear_color=_get_random_color(rng) + (1,),
+                forward_transforms=True,
             )
             rtt.add_color_textures(rtt_tex)
             rtt_render = ngl.RenderTexture(