scene_video_render

场景的渲染，其实就是对其下的所有对象引用计数加1，然后调用其对象的渲染函数，最后再引用计数减1.

static void scene_video_render(void *data, gs_effect_t *effect)
{
    DARRAY(struct obs_scene_item *) remove_items;
    struct obs_scene *scene = data;
    struct obs_scene_item *item;

    da_init(remove_items);
    video_lock(scene);
    if (!scene->is_group) {
        update_transforms_and_prune_sources(scene, &remove_items.da,NULL);
    }

    gs_blend_state_push();
    gs_reset_blend_state();

    item = scene->first_item;
    while (item) {
        if (item->user_visible || transition_active(item->hide_transition)) {
            render_item(item);
        }
        item = item->next;
    }
    gs_blend_state_pop();
    video_unlock(scene);

    for (size_t i = 0; i < remove_items.num; i++)
    {
        obs_sceneitem_release(remove_items.array[i]);
    }

    da_free(remove_items);
    UNUSED_PARAMETER(effect);
}

所以渲染的过程其实就是各对象的渲染过程。

static inline void render_item(struct obs_scene_item *item)
{
    GS_DEBUG_MARKER_BEGIN_FORMAT(GS_DEBUG_COLOR_ITEM, "Item: %s",  obs_source_get_name(item->source));

    if (item->item_render) {
        uint32_t width = obs_source_get_width(item->source);
        uint32_t height = obs_source_get_height(item->source);

        if (!width || !height) {
            goto cleanup;
        }

        uint32_t cx = calc_cx(item, width);
        uint32_t cy = calc_cy(item, height);

        if (cx && cy && gs_texrender_begin(item->item_render, cx, cy))
        {
            float cx_scale = (float)width / (float)cx;
            float cy_scale = (float)height / (float)cy;
            struct vec4 clear_color;

            vec4_zero(&clear_color);
            gs_clear(GS_CLEAR_COLOR, &clear_color, 0.0f, 0);
            gs_ortho(0.0f, (float)width, 0.0f, (float)height, -100.0f, 100.0f);

            gs_matrix_scale3f(cx_scale, cy_scale, 1.0f);
            gs_matrix_translate3f(-(float)item->crop.left, -(float)item->crop.top, 0.0f);

            if (item->user_visible && transition_active(item->show_transition))
            {
                const int cx =obs_source_get_width(item->source);
                const int cy =obs_source_get_height(item->source);
                obs_transition_set_size(item->show_transition,cx, cy);
                obs_source_video_render(item->show_transition);
            } else if (!item->user_visible &&transition_active(item->hide_transition))
            {
                const int cx =obs_source_get_width(item->source);
                const int cy =obs_source_get_height(item->source);
                obs_transition_set_size(item->hide_transition,cx, cy);
                obs_source_video_render(item->hide_transition);
            } else {
                obs_source_set_texcoords_centered(item->source,true);
                obs_source_video_render(item->source);
                obs_source_set_texcoords_centered(item->source,false);
            }

            gs_texrender_end(item->item_render);
        }
    }

    const bool previous = gs_set_linear_srgb(true);
    gs_matrix_push();
    gs_matrix_mul(&item->draw_transform);
    if (item->item_render){
        render_item_texture(item);
    }
    else if (item->user_visible && transition_active(item->show_transition)) {
        const int cx = obs_source_get_width(item->source);
        const int cy = obs_source_get_height(item->source);
        obs_transition_set_size(item->show_transition, cx, cy);
        obs_source_video_render(item->show_transition);
    } else if (!item->user_visible &&transition_active(item->hide_transition)) {
        const int cx = obs_source_get_width(item->source);
        const int cy = obs_source_get_height(item->source);
        obs_transition_set_size(item->hide_transition, cx, cy);
        obs_source_video_render(item->hide_transition);
    } else {
        const bool centered =are_texcoords_centered(&item->draw_transform);
        obs_source_set_texcoords_centered(item->source, centered);
        obs_source_video_render(item->source);
        obs_source_set_texcoords_centered(item->source, false);
    }
    gs_matrix_pop();
    gs_set_linear_srgb(previous);

cleanup:
    GS_DEBUG_MARKER_END();
}