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GPencil: Implement Holdout materials 

This new feature allows to use the strokes as an eraser of any stroke below. This is very handy to open holes in filled areas.

After running some tests, we have decided to keep the additive effect of the holdout color. To get clean holdout areas, just move the color to black to remove any additive effect. To have additive effect can be used in situations like tint slightly a transparent window with blue to simulate the glass.

See T79878 for more details

Differential Revision: https://developer.blender.org/D8932
This commit is contained in:
Antonio Vazquez 2020-09-18 18:23:25 +02:00
parent 7b988188dc
commit 0335c1fd21
Notes: blender-bot 2023-02-13 21:28:17 +01:00 
Referenced by issue #81013, In Weight Paint mode, draw error when using X-Ray + Clipping Region
Referenced by issue #79878, GPencil: Add Holdout material option to open holes in filled areas
9 changed files with 99 additions and 46 deletions
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5
release/scripts/startup/bl_ui/properties_material_gpencil.py
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@ -70,6 +70,7 @@ class GPENCIL_UL_matslots(UIList):
row.prop(ma, "name", text="", emboss=False, icon_value=icon)
row = layout.row(align=True)
if gpcolor.ghost is True:
icon = 'ONIONSKIN_OFF'
else:
@ -168,6 +169,8 @@ class MATERIAL_PT_gpencil_strokecolor(GPMaterialButtonsPanel, Panel):
if gpcolor.mode == 'LINE':
col.prop(gpcolor, "use_overlap_strokes")
col.prop(gpcolor, "use_stroke_holdout")
class MATERIAL_PT_gpencil_fillcolor(GPMaterialButtonsPanel, Panel):
bl_label = "Fill"
@ -222,6 +225,8 @@ class MATERIAL_PT_gpencil_fillcolor(GPMaterialButtonsPanel, Panel):
col.prop(gpcolor, "texture_scale", text="Scale")
col.prop(gpcolor, "texture_clamp", text="Clip Image")
col.prop(gpcolor, "use_fill_holdout")
class MATERIAL_PT_gpencil_preview(GPMaterialButtonsPanel, Panel):
bl_label = "Preview"

11
source/blender/draw/engines/gpencil/gpencil_cache_utils.c
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@ -58,6 +58,17 @@ GPENCIL_tObject *gpencil_object_cache_add(GPENCIL_PrivateData *pd, Object *ob)
tgp_ob->is_drawmode3d = (gpd->draw_mode == GP_DRAWMODE_3D) || pd->draw_depth_only;
tgp_ob->object_scale = mat4_to_scale(ob->obmat);
/* Check if any material with holdout flag enabled. */
tgp_ob->do_mat_holdout = false;
for (int i = 0; i < ob->totcol; i++) {
MaterialGPencilStyle *gp_style = BKE_gpencil_material_settings(ob, i + 1);
if ((gp_style->flag & GP_MATERIAL_IS_STROKE_HOLDOUT) ||
((gp_style->flag & GP_MATERIAL_IS_FILL_HOLDOUT))) {
tgp_ob->do_mat_holdout = true;
break;
}
}
/* Find the normal most likely to represent the gpObject. */
/* TODO: This does not work quite well if you use
* strokes not aligned with the object axes. Maybe we could try to

8
source/blender/draw/engines/gpencil/gpencil_draw_data.c
View File

@ -237,6 +237,14 @@ GPENCIL_MaterialPool *gpencil_material_pool_create(GPENCIL_PrivateData *pd, Obje
mat_data->flag |= GP_STROKE_OVERLAP;
}
/* Material with holdout. */
if (gp_style->flag & GP_MATERIAL_IS_STROKE_HOLDOUT) {
mat_data->flag |= GP_STROKE_HOLDOUT;
}
if (gp_style->flag & GP_MATERIAL_IS_FILL_HOLDOUT) {
mat_data->flag |= GP_FILL_HOLDOUT;
}
gp_style = gpencil_viewport_material_overrides(pd, ob, color_type, gp_style);
/* Stroke Style */

6
source/blender/draw/engines/gpencil/gpencil_engine.h
View File

@ -80,6 +80,8 @@ typedef struct gpMaterial {
#define GP_STROKE_TEXTURE_STENCIL (1 << 4)
#define GP_STROKE_TEXTURE_PREMUL (1 << 5)
#define GP_STROKE_DOTS (1 << 6)
#define GP_STROKE_HOLDOUT (1 << 7)
#define GP_FILL_HOLDOUT (1 << 8)
#define GP_FILL_TEXTURE_USE (1 << 10)
#define GP_FILL_TEXTURE_PREMUL (1 << 11)
#define GP_FILL_TEXTURE_CLIP (1 << 12)
@ -194,6 +196,10 @@ typedef struct GPENCIL_tObject {
float plane_mat[4][4];
bool is_drawmode3d;
/* Use Material Holdout. */
bool do_mat_holdout;
} GPENCIL_tObject;
/* *********** LISTS *********** */

74
source/blender/draw/engines/gpencil/gpencil_shader_fx.c
View File

@ -585,10 +585,6 @@ void gpencil_vfx_cache_populate(GPENCIL_Data *vedata, Object *ob, GPENCIL_tObjec
bGPdata *gpd = (bGPdata *)ob->data;
GPENCIL_FramebufferList *fbl = vedata->fbl;
GPENCIL_PrivateData *pd = vedata->stl->pd;
/* If simplify enabled, nothing more to do. */
if (pd->simplify_fx) {
return;
}
/* These may not be allocated yet, use adress of future pointer. */
gpIterVfxData iter = {
@ -601,44 +597,46 @@ void gpencil_vfx_cache_populate(GPENCIL_Data *vedata, Object *ob, GPENCIL_tObjec
.target_reveal_tx = &pd->reveal_layer_tx,
.source_reveal_tx = &pd->reveal_object_tx,
};
LISTBASE_FOREACH (ShaderFxData *, fx, &ob->shader_fx) {
if (effect_is_active(gpd, fx, pd->is_viewport)) {
switch (fx->type) {
case eShaderFxType_Blur:
gpencil_vfx_blur((BlurShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Colorize:
gpencil_vfx_colorize((ColorizeShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Flip:
gpencil_vfx_flip((FlipShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Pixel:
gpencil_vfx_pixelize((PixelShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Rim:
gpencil_vfx_rim((RimShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Shadow:
gpencil_vfx_shadow((ShadowShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Glow:
gpencil_vfx_glow((GlowShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Swirl:
gpencil_vfx_swirl((SwirlShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Wave:
gpencil_vfx_wave((WaveShaderFxData *)fx, ob, &iter);
break;
default:
break;
/* If simplify enabled, nothing more to do. */
if (!pd->simplify_fx) {
LISTBASE_FOREACH (ShaderFxData *, fx, &ob->shader_fx) {
if (effect_is_active(gpd, fx, pd->is_viewport)) {
switch (fx->type) {
case eShaderFxType_Blur:
gpencil_vfx_blur((BlurShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Colorize:
gpencil_vfx_colorize((ColorizeShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Flip:
gpencil_vfx_flip((FlipShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Pixel:
gpencil_vfx_pixelize((PixelShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Rim:
gpencil_vfx_rim((RimShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Shadow:
gpencil_vfx_shadow((ShadowShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Glow:
gpencil_vfx_glow((GlowShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Swirl:
gpencil_vfx_swirl((SwirlShaderFxData *)fx, ob, &iter);
break;
case eShaderFxType_Wave:
gpencil_vfx_wave((WaveShaderFxData *)fx, ob, &iter);
break;
default:
break;
}
}
}
}
if (tgp_ob->vfx.first != NULL) {
if ((!pd->simplify_fx && tgp_ob->vfx.first != NULL) || tgp_ob->do_mat_holdout) {
/* We need an extra pass to combine result to main buffer. */
iter.target_fb = &fbl->gpencil_fb;

4
source/blender/draw/engines/gpencil/shaders/gpencil_common_lib.glsl
View File

@ -34,6 +34,8 @@ struct gpMaterial {
#define GP_STROKE_TEXTURE_STENCIL (1 << 4)
#define GP_STROKE_TEXTURE_PREMUL (1 << 5)
#define GP_STROKE_DOTS (1 << 6)
#define GP_STROKE_HOLDOUT (1 << 7)
#define GP_FILL_HOLDOUT (1 << 8)
#define GP_FILL_TEXTURE_USE (1 << 10)
#define GP_FILL_TEXTURE_PREMUL (1 << 11)
#define GP_FILL_TEXTURE_CLIP (1 << 12)
@ -44,7 +46,7 @@ struct gpMaterial {
/* Multiline defines can crash blender with certain GPU drivers. */
/* clang-format off */
#define GP_FILL_FLAGS (GP_FILL_TEXTURE_USE | GP_FILL_TEXTURE_PREMUL | GP_FILL_TEXTURE_CLIP | GP_FILL_GRADIENT_USE | GP_FILL_GRADIENT_RADIAL)
#define GP_FILL_FLAGS (GP_FILL_TEXTURE_USE | GP_FILL_TEXTURE_PREMUL | GP_FILL_TEXTURE_CLIP | GP_FILL_GRADIENT_USE | GP_FILL_GRADIENT_RADIAL | GP_FILL_HOLDOUT)
/* clang-format on */
#define GP_FLAG_TEST(flag, val) (((flag) & (val)) != 0)

21
source/blender/draw/engines/gpencil/shaders/gpencil_frag.glsl
View File

@ -89,14 +89,21 @@ void main()
fragColor *= stroke_round_cap_mask(
strokePt1, strokePt2, strokeAspect, strokeThickness, strokeHardeness);
/* For compatibility with colored alpha buffer.
* Note that we are limited to mono-chromatic alpha blending here
* because of the blend equation and the limit of 1 color target
* when using custom color blending. */
revealColor = vec4(0.0, 0.0, 0.0, fragColor.a);
/* Holdout materials. */
if (GP_FLAG_TEST(matFlag, GP_STROKE_HOLDOUT | GP_FILL_HOLDOUT)) {
revealColor = fragColor.aaaa;
}
else {
/* NOT holdout materials.
* For compatibility with colored alpha buffer.
* Note that we are limited to mono-chromatic alpha blending here
* because of the blend equation and the limit of 1 color target
* when using custom color blending. */
revealColor = vec4(0.0, 0.0, 0.0, fragColor.a);
if (fragColor.a < 0.001) {
discard;
if (fragColor.a < 0.001) {
discard;
}
}
vec2 fb_size = max(vec2(textureSize(gpSceneDepthTexture, 0).xy),

4
source/blender/makesdna/DNA_material_types.h
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@ -128,6 +128,10 @@ typedef enum eMaterialGPencilStyle_Flag {
GP_MATERIAL_STROKE_TEX_MIX = (1 << 11),
/* disable stencil clipping (overlap) */
GP_MATERIAL_DISABLE_STENCIL = (1 << 12),
/* Material used as stroke masking. */
GP_MATERIAL_IS_STROKE_HOLDOUT = (1 << 13),
/* Material used as fill masking. */
GP_MATERIAL_IS_FILL_HOLDOUT = (1 << 14),
} eMaterialGPencilStyle_Flag;
typedef enum eMaterialGPencilStyle_Mode {

12
source/blender/makesrna/intern/rna_material.c
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@ -564,6 +564,18 @@ static void rna_def_material_greasepencil(BlenderRNA *brna)
prop, "Self Overlap", "Disable stencil and overlap self intersections with alpha materials");
RNA_def_property_update(prop, NC_GPENCIL | ND_SHADING, "rna_MaterialGpencil_update");
prop = RNA_def_property(srna, "use_stroke_holdout", PROP_BOOLEAN, PROP_NONE);
RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_MATERIAL_IS_STROKE_HOLDOUT);
RNA_def_property_ui_text(
prop, "Holdout", "Remove the color from underneath strokes using current stroke as mask");
RNA_def_property_update(prop, NC_GPENCIL | ND_SHADING, "rna_MaterialGpencil_update");
prop = RNA_def_property(srna, "use_fill_holdout", PROP_BOOLEAN, PROP_NONE);
RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_MATERIAL_IS_FILL_HOLDOUT);
RNA_def_property_ui_text(
prop, "Holdout", "Remove the color from underneath strokes using current stroke as mask");
RNA_def_property_update(prop, NC_GPENCIL | ND_SHADING, "rna_MaterialGpencil_update");
prop = RNA_def_property(srna, "show_stroke", PROP_BOOLEAN, PROP_NONE);
RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_MATERIAL_STROKE_SHOW);
RNA_def_property_ui_text(prop, "Show Stroke", "Show stroke lines of this material");