[Mesa-dev] [PATCH v2] i965/gen8: Fix antialiased line rendering with width < 1.5

Iago Toral Quiroga itoral at igalia.com
Thu Jun 11 00:50:53 PDT 2015


The same fix Marius implemented for gen6 (commit a9b04d8a) and
gen7 (commit 24ecf37a).

Also, we need the same code to handle special cases of line width
in gen6, gen7 and now gen8, so put that in the helper function
we use to compute the line width.
---
 src/mesa/drivers/dri/i965/brw_util.h      | 31 +++++++++++++++++++++++++++----
 src/mesa/drivers/dri/i965/gen6_sf_state.c | 22 +---------------------
 src/mesa/drivers/dri/i965/gen7_sf_state.c | 21 +--------------------
 src/mesa/drivers/dri/i965/gen8_sf_state.c |  5 +----
 4 files changed, 30 insertions(+), 49 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_util.h b/src/mesa/drivers/dri/i965/brw_util.h
index 671d72e..04e4e94 100644
--- a/src/mesa/drivers/dri/i965/brw_util.h
+++ b/src/mesa/drivers/dri/i965/brw_util.h
@@ -41,7 +41,7 @@ extern GLuint brw_translate_blend_factor( GLenum factor );
 extern GLuint brw_translate_blend_equation( GLenum mode );
 extern GLenum brw_fix_xRGB_alpha(GLenum function);
 
-static inline float
+static inline uint32_t
 brw_get_line_width(struct brw_context *brw)
 {
    /* From the OpenGL 4.4 spec:
@@ -50,9 +50,32 @@ brw_get_line_width(struct brw_context *brw)
     * the supplied width to the nearest integer, then clamping it to the
     * implementation-dependent maximum non-antialiased line width."
     */
-   return CLAMP(!brw->ctx.Multisample._Enabled && !brw->ctx.Line.SmoothFlag
-                ? roundf(brw->ctx.Line.Width) : brw->ctx.Line.Width,
-                0.0, brw->ctx.Const.MaxLineWidth);
+   float line_width =
+      CLAMP(!brw->ctx.Multisample._Enabled && !brw->ctx.Line.SmoothFlag
+            ? roundf(brw->ctx.Line.Width) : brw->ctx.Line.Width,
+            0.0, brw->ctx.Const.MaxLineWidth);
+   uint32_t line_width_u3_7 = U_FIXED(line_width, 7);
+
+   /* Line width of 0 is not allowed when MSAA enabled */
+   if (brw->ctx.Multisample._Enabled) {
+      if (line_width_u3_7 == 0)
+         line_width_u3_7 = 1;
+   } else if (brw->ctx.Line.SmoothFlag && line_width < 1.5) {
+      /* For 1 pixel line thickness or less, the general
+       * anti-aliasing algorithm gives up, and a garbage line is
+       * generated.  Setting a Line Width of 0.0 specifies the
+       * rasterization of the "thinnest" (one-pixel-wide),
+       * non-antialiased lines.
+       *
+       * Lines rendered with zero Line Width are rasterized using
+       * Grid Intersection Quantization rules as specified by
+       * bspec section 6.3.12.1 Zero-Width (Cosmetic) Line
+       * Rasterization.
+       */
+      line_width_u3_7 = 0;
+   }
+
+   return line_width_u3_7;
 }
 
 #endif
diff --git a/src/mesa/drivers/dri/i965/gen6_sf_state.c b/src/mesa/drivers/dri/i965/gen6_sf_state.c
index d577764..5809628 100644
--- a/src/mesa/drivers/dri/i965/gen6_sf_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_sf_state.c
@@ -361,27 +361,7 @@ upload_sf_state(struct brw_context *brw)
 
    /* _NEW_LINE */
    {
-      float line_width = brw_get_line_width(brw);
-      uint32_t line_width_u3_7 = U_FIXED(line_width, 7);
-
-      /* Line width of 0 is not allowed when MSAA enabled */
-      if (ctx->Multisample._Enabled) {
-         if (line_width_u3_7 == 0)
-             line_width_u3_7 = 1;
-      } else if (ctx->Line.SmoothFlag && ctx->Line.Width < 1.5) {
-         /* For 1 pixel line thickness or less, the general
-          * anti-aliasing algorithm gives up, and a garbage line is
-          * generated.  Setting a Line Width of 0.0 specifies the
-          * rasterization of the "thinnest" (one-pixel-wide),
-          * non-antialiased lines.
-          *
-          * Lines rendered with zero Line Width are rasterized using
-          * Grid Intersection Quantization rules as specified by
-          * bspec section 6.3.12.1 Zero-Width (Cosmetic) Line
-          * Rasterization.
-          */
-         line_width_u3_7 = 0;
-      }
+      uint32_t line_width_u3_7 = brw_get_line_width(brw);
       dw3 |= line_width_u3_7 << GEN6_SF_LINE_WIDTH_SHIFT;
    }
    if (ctx->Line.SmoothFlag) {
diff --git a/src/mesa/drivers/dri/i965/gen7_sf_state.c b/src/mesa/drivers/dri/i965/gen7_sf_state.c
index 87ff284..a20967c 100644
--- a/src/mesa/drivers/dri/i965/gen7_sf_state.c
+++ b/src/mesa/drivers/dri/i965/gen7_sf_state.c
@@ -192,26 +192,7 @@ upload_sf_state(struct brw_context *brw)
 
    /* _NEW_LINE */
    {
-      float line_width = brw_get_line_width(brw);
-      uint32_t line_width_u3_7 = U_FIXED(line_width, 7);
-      /* Line width of 0 is not allowed when MSAA enabled */
-      if (ctx->Multisample._Enabled) {
-         if (line_width_u3_7 == 0)
-             line_width_u3_7 = 1;
-      } else if (ctx->Line.SmoothFlag && ctx->Line.Width < 1.5) {
-         /* For 1 pixel line thickness or less, the general
-          * anti-aliasing algorithm gives up, and a garbage line is
-          * generated.  Setting a Line Width of 0.0 specifies the
-          * rasterization of the "thinnest" (one-pixel-wide),
-          * non-antialiased lines.
-          *
-          * Lines rendered with zero Line Width are rasterized using
-          * Grid Intersection Quantization rules as specified by
-          * bspec section 6.3.12.1 Zero-Width (Cosmetic) Line
-          * Rasterization.
-          */
-         line_width_u3_7 = 0;
-      }
+      uint32_t line_width_u3_7 = brw_get_line_width(brw);
       dw2 |= line_width_u3_7 << GEN6_SF_LINE_WIDTH_SHIFT;
    }
    if (ctx->Line.SmoothFlag) {
diff --git a/src/mesa/drivers/dri/i965/gen8_sf_state.c b/src/mesa/drivers/dri/i965/gen8_sf_state.c
index 83ef62b..c2b585d 100644
--- a/src/mesa/drivers/dri/i965/gen8_sf_state.c
+++ b/src/mesa/drivers/dri/i965/gen8_sf_state.c
@@ -154,10 +154,7 @@ upload_sf(struct brw_context *brw)
        dw1 |= GEN6_SF_VIEWPORT_TRANSFORM_ENABLE;
 
    /* _NEW_LINE */
-   float line_width = brw_get_line_width(brw);
-   uint32_t line_width_u3_7 = U_FIXED(line_width, 7);
-   if (line_width_u3_7 == 0)
-      line_width_u3_7 = 1;
+   uint32_t line_width_u3_7 = brw_get_line_width(brw);
    if (brw->gen >= 9 || brw->is_cherryview) {
       dw1 |= line_width_u3_7 << GEN9_SF_LINE_WIDTH_SHIFT;
    } else {
-- 
1.9.1



More information about the mesa-dev mailing list